From: Ovidiu Panait ovidiu.panait@windriver.com
stable inclusion from linux-4.19.193 commit b190383c714a379002b00bc8de43371e78d291d8
--------------------------------
After the backport of the changes to fix CVE 2019-7308, the selftests also need to be fixed up, as was done originally in mainline 80c9b2fae87b ("bpf: add various test cases to selftests").
This is a backport of upstream commit 80c9b2fae87b ("bpf: add various test cases to selftests") adapted to 4.19 in order to fix the selftests that began to fail after CVE-2019-7308 fixes.
Suggested-by: Frank van der Linden fllinden@amazon.com Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- tools/testing/selftests/bpf/test_verifier.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index 9db5a7378f40f..fef1c9e3c4b81 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -2448,6 +2448,7 @@ static struct bpf_test tests[] = { }, .result = REJECT, .errstr = "invalid stack off=-79992 size=8", + .errstr_unpriv = "R1 stack pointer arithmetic goes out of range", }, { "PTR_TO_STACK store/load - out of bounds high", @@ -2844,6 +2845,8 @@ static struct bpf_test tests[] = { BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0, -8), BPF_EXIT_INSN(), }, + .errstr_unpriv = "R1 stack pointer arithmetic goes out of range", + .result_unpriv = REJECT, .result = ACCEPT, }, { @@ -7457,6 +7460,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", + .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7481,6 +7485,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", + .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7507,6 +7512,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", + .errstr_unpriv = "R8 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7532,6 +7538,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", + .errstr_unpriv = "R8 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7580,6 +7587,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", + .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7651,6 +7659,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", + .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7702,6 +7711,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", + .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7729,6 +7739,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", + .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7755,6 +7766,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", + .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7784,6 +7796,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", + .errstr_unpriv = "R7 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7814,6 +7827,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 4 }, .errstr = "R0 invalid mem access 'inv'", + .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7842,6 +7856,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", + .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, .result_unpriv = REJECT, }, @@ -7894,6 +7909,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "R0 min value is negative, either use unsigned index or do a if (index >=0) check.", + .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -8266,6 +8282,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "pointer offset 1073741822", + .errstr_unpriv = "R0 pointer arithmetic of map value goes out of range", .result = REJECT }, { @@ -8287,6 +8304,7 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "pointer offset -1073741822", + .errstr_unpriv = "R0 pointer arithmetic of map value goes out of range", .result = REJECT }, { @@ -8458,6 +8476,7 @@ static struct bpf_test tests[] = { BPF_EXIT_INSN() }, .errstr = "fp pointer offset 1073741822", + .errstr_unpriv = "R1 stack pointer arithmetic goes out of range", .result = REJECT }, {
From: Piotr Krysiuk piotras@gmail.com
stable inclusion from linux-4.19.193 commit 1982f436a9a990e338ac4d7ed80a9fb40e0a1885
--------------------------------
commit 0a13e3537ea67452d549a6a80da3776d6b7dedb3 upstream
Fix up test_verifier error messages for the case where the original error message changed, or for the case where pointer alu errors differ between privileged and unprivileged tests. Also, add alternative tests for keeping coverage of the original verifier rejection error message (fp alu), and newly reject map_ptr += rX where rX == 0 given we now forbid alu on these types for unprivileged. All test_verifier cases pass after the change. The test case fixups were kept separate to ease backporting of core changes.
Signed-off-by: Piotr Krysiuk piotras@gmail.com Co-developed-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Alexei Starovoitov ast@kernel.org [OP: backport to 4.19, skipping non-existent tests] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- tools/testing/selftests/bpf/test_verifier.c | 42 ++++++++++++++++----- 1 file changed, 33 insertions(+), 9 deletions(-)
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index fef1c9e3c4b81..29d42f7796d9d 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -2837,7 +2837,7 @@ static struct bpf_test tests[] = { .result = ACCEPT, }, { - "unpriv: adding of fp", + "unpriv: adding of fp, reg", .insns = { BPF_MOV64_IMM(BPF_REG_0, 0), BPF_MOV64_IMM(BPF_REG_1, 0), @@ -2845,6 +2845,19 @@ static struct bpf_test tests[] = { BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0, -8), BPF_EXIT_INSN(), }, + .errstr_unpriv = "R1 tried to add from different maps, paths, or prohibited types", + .result_unpriv = REJECT, + .result = ACCEPT, + }, + { + "unpriv: adding of fp, imm", + .insns = { + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, 0), + BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0, -8), + BPF_EXIT_INSN(), + }, .errstr_unpriv = "R1 stack pointer arithmetic goes out of range", .result_unpriv = REJECT, .result = ACCEPT, @@ -9758,8 +9771,9 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1), BPF_EXIT_INSN(), }, - .result = REJECT, + .errstr_unpriv = "R0 tried to sub from different maps, paths, or prohibited types", .errstr = "R0 tried to subtract pointer from scalar", + .result = REJECT, }, { "check deducing bounds from const, 2", @@ -9772,6 +9786,8 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_1, BPF_REG_0), BPF_EXIT_INSN(), }, + .errstr_unpriv = "R1 tried to sub from different maps, paths, or prohibited types", + .result_unpriv = REJECT, .result = ACCEPT, .retval = 1, }, @@ -9783,8 +9799,9 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1), BPF_EXIT_INSN(), }, - .result = REJECT, + .errstr_unpriv = "R0 tried to sub from different maps, paths, or prohibited types", .errstr = "R0 tried to subtract pointer from scalar", + .result = REJECT, }, { "check deducing bounds from const, 4", @@ -9797,6 +9814,8 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_1, BPF_REG_0), BPF_EXIT_INSN(), }, + .errstr_unpriv = "R1 tried to sub from different maps, paths, or prohibited types", + .result_unpriv = REJECT, .result = ACCEPT, }, { @@ -9807,8 +9826,9 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1), BPF_EXIT_INSN(), }, - .result = REJECT, + .errstr_unpriv = "R0 tried to sub from different maps, paths, or prohibited types", .errstr = "R0 tried to subtract pointer from scalar", + .result = REJECT, }, { "check deducing bounds from const, 6", @@ -9819,8 +9839,9 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1), BPF_EXIT_INSN(), }, - .result = REJECT, + .errstr_unpriv = "R0 tried to sub from different maps, paths, or prohibited types", .errstr = "R0 tried to subtract pointer from scalar", + .result = REJECT, }, { "check deducing bounds from const, 7", @@ -9832,8 +9853,9 @@ static struct bpf_test tests[] = { offsetof(struct __sk_buff, mark)), BPF_EXIT_INSN(), }, - .result = REJECT, + .errstr_unpriv = "R1 tried to sub from different maps, paths, or prohibited types", .errstr = "dereference of modified ctx ptr", + .result = REJECT, }, { "check deducing bounds from const, 8", @@ -9845,8 +9867,9 @@ static struct bpf_test tests[] = { offsetof(struct __sk_buff, mark)), BPF_EXIT_INSN(), }, - .result = REJECT, + .errstr_unpriv = "R1 tried to add from different maps, paths, or prohibited types", .errstr = "dereference of modified ctx ptr", + .result = REJECT, }, { "check deducing bounds from const, 9", @@ -9856,8 +9879,9 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1), BPF_EXIT_INSN(), }, - .result = REJECT, + .errstr_unpriv = "R0 tried to sub from different maps, paths, or prohibited types", .errstr = "R0 tried to subtract pointer from scalar", + .result = REJECT, }, { "check deducing bounds from const, 10", @@ -9869,8 +9893,8 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1), BPF_EXIT_INSN(), }, - .result = REJECT, .errstr = "math between ctx pointer and register with unbounded min value is not allowed", + .result = REJECT, }, { "bpf_exit with invalid return code. test1",
From: Andrey Ignatov rdna@fb.com
stable inclusion from linux-4.19.193 commit 737f5f3a633518feae7b2793f4666c67e39bcc5a
--------------------------------
commit 6c2afb674dbda9b736b8f09c976516e1e788860a upstream
Test the following narrow loads in test_verifier for context __sk_buff: * off=1, size=1 - ok; * off=2, size=1 - ok; * off=3, size=1 - ok; * off=0, size=2 - ok; * off=1, size=2 - fail; * off=0, size=2 - ok; * off=3, size=2 - fail.
Signed-off-by: Andrey Ignatov rdna@fb.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- tools/testing/selftests/bpf/test_verifier.c | 48 ++++++++++++++++----- 1 file changed, 38 insertions(+), 10 deletions(-)
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index 29d42f7796d9d..fdc093f298189 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -2002,29 +2002,27 @@ static struct bpf_test tests[] = { .result = ACCEPT, }, { - "check skb->hash byte load not permitted 1", + "check skb->hash byte load permitted 1", .insns = { BPF_MOV64_IMM(BPF_REG_0, 0), BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_1, offsetof(struct __sk_buff, hash) + 1), BPF_EXIT_INSN(), }, - .errstr = "invalid bpf_context access", - .result = REJECT, + .result = ACCEPT, }, { - "check skb->hash byte load not permitted 2", + "check skb->hash byte load permitted 2", .insns = { BPF_MOV64_IMM(BPF_REG_0, 0), BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_1, offsetof(struct __sk_buff, hash) + 2), BPF_EXIT_INSN(), }, - .errstr = "invalid bpf_context access", - .result = REJECT, + .result = ACCEPT, }, { - "check skb->hash byte load not permitted 3", + "check skb->hash byte load permitted 3", .insns = { BPF_MOV64_IMM(BPF_REG_0, 0), #if __BYTE_ORDER == __LITTLE_ENDIAN @@ -2036,8 +2034,7 @@ static struct bpf_test tests[] = { #endif BPF_EXIT_INSN(), }, - .errstr = "invalid bpf_context access", - .result = REJECT, + .result = ACCEPT, }, { "check cb access: byte, wrong type", @@ -2149,7 +2146,7 @@ static struct bpf_test tests[] = { .result = ACCEPT, }, { - "check skb->hash half load not permitted", + "check skb->hash half load permitted 2", .insns = { BPF_MOV64_IMM(BPF_REG_0, 0), #if __BYTE_ORDER == __LITTLE_ENDIAN @@ -2158,6 +2155,37 @@ static struct bpf_test tests[] = { #else BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1, offsetof(struct __sk_buff, hash)), +#endif + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + }, + { + "check skb->hash half load not permitted, unaligned 1", + .insns = { + BPF_MOV64_IMM(BPF_REG_0, 0), +#if __BYTE_ORDER == __LITTLE_ENDIAN + BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1, + offsetof(struct __sk_buff, hash) + 1), +#else + BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1, + offsetof(struct __sk_buff, hash) + 3), +#endif + BPF_EXIT_INSN(), + }, + .errstr = "invalid bpf_context access", + .result = REJECT, + }, + { + "check skb->hash half load not permitted, unaligned 3", + .insns = { + BPF_MOV64_IMM(BPF_REG_0, 0), +#if __BYTE_ORDER == __LITTLE_ENDIAN + BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1, + offsetof(struct __sk_buff, hash) + 3), +#else + BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1, + offsetof(struct __sk_buff, hash) + 1), #endif BPF_EXIT_INSN(), },
From: Ovidiu Panait ovidiu.panait@windriver.com
stable inclusion from linux-4.19.193 commit c905bfe767e98a13dd886bf241ba9ee0640a53ff
--------------------------------
Backport the missing selftest part of commit 7da6cd690c43 ("bpf: improve verifier branch analysis") in order to fix the following test_verifier failures:
... Unexpected success to load! 0: (b7) r0 = 0 1: (75) if r0 s>= 0x0 goto pc+1 3: (95) exit processed 3 insns (limit 131072), stack depth 0 Unexpected success to load! 0: (b7) r0 = 0 1: (75) if r0 s>= 0x0 goto pc+1 3: (95) exit processed 3 insns (limit 131072), stack depth 0 ...
The changesets apply with a minor context difference.
Fixes: 7da6cd690c43 ("bpf: improve verifier branch analysis") Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- tools/testing/selftests/bpf/test_verifier.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index fdc093f298189..a34552aadc129 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -7867,7 +7867,7 @@ static struct bpf_test tests[] = { BPF_JMP_IMM(BPF_JA, 0, 0, -7), }, .fixup_map1 = { 4 }, - .errstr = "R0 invalid mem access 'inv'", + .errstr = "unbounded min value", .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, @@ -9850,7 +9850,7 @@ static struct bpf_test tests[] = { "check deducing bounds from const, 5", .insns = { BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_JMP_IMM(BPF_JSGE, BPF_REG_0, 0, 1), + BPF_JMP_IMM(BPF_JSGE, BPF_REG_0, 1, 1), BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1), BPF_EXIT_INSN(), },
From: Alexei Starovoitov ast@kernel.org
stable inclusion from linux-4.19.193 commit e0b86677fb3e4622b444dcdd8546caa0dba8a689
--------------------------------
commit fb8d251ee2a6bf4d7f4af5548e9c8f4fb5f90402 upstream
This patch extends is_branch_taken() logic from JMP+K instructions to JMP+X instructions. Conditional branches are often done when src and dst registers contain known scalars. In such case the verifier can follow the branch that is going to be taken when program executes. That speeds up the verification and is essential feature to support bounded loops.
Signed-off-by: Alexei Starovoitov ast@kernel.org Acked-by: Andrii Nakryiko andriin@fb.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net [OP: drop is_jmp32 parameter from is_branch_taken() calls and adjust context] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- kernel/bpf/verifier.c | 33 ++++++++++++++++++--------------- 1 file changed, 18 insertions(+), 15 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 1efbf7e684fde..08772c69edb18 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4415,9 +4415,10 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, struct bpf_verifier_state *this_branch = env->cur_state; struct bpf_verifier_state *other_branch; struct bpf_reg_state *regs = this_branch->frame[this_branch->curframe]->regs; - struct bpf_reg_state *dst_reg, *other_branch_regs; + struct bpf_reg_state *dst_reg, *other_branch_regs, *src_reg = NULL; u8 opcode = BPF_OP(insn->code); bool is_jmp32; + int pred = -1; int err;
/* Only conditional jumps are expected to reach here. */ @@ -4442,6 +4443,7 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, insn->src_reg); return -EACCES; } + src_reg = ®s[insn->src_reg]; } else { if (insn->src_reg != BPF_REG_0) { verbose(env, "BPF_JMP/JMP32 uses reserved fields\n"); @@ -4457,20 +4459,21 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, dst_reg = ®s[insn->dst_reg]; is_jmp32 = BPF_CLASS(insn->code) == BPF_JMP32;
- if (BPF_SRC(insn->code) == BPF_K) { - int pred = is_branch_taken(dst_reg, insn->imm, opcode, - is_jmp32); - - if (pred == 1) { - /* only follow the goto, ignore fall-through */ - *insn_idx += insn->off; - return 0; - } else if (pred == 0) { - /* only follow fall-through branch, since - * that's where the program will go - */ - return 0; - } + if (BPF_SRC(insn->code) == BPF_K) + pred = is_branch_taken(dst_reg, insn->imm, opcode, is_jmp32); + else if (src_reg->type == SCALAR_VALUE && + tnum_is_const(src_reg->var_off)) + pred = is_branch_taken(dst_reg, src_reg->var_off.value, + opcode, is_jmp32); + if (pred == 1) { + /* only follow the goto, ignore fall-through */ + *insn_idx += insn->off; + return 0; + } else if (pred == 0) { + /* only follow fall-through branch, since + * that's where the program will go + */ + return 0; }
other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx,
From: John Fastabend john.fastabend@gmail.com
stable inclusion from linux-4.19.193 commit f915e7975fc2d593ddb60b67d14eef314eb6dd08
--------------------------------
commit 9ac26e9973bac5716a2a542e32f380c84db2b88c upstream.
With current ALU32 subreg handling and retval refine fix from last patches we see an expected failure in test_verifier. With verbose verifier state being printed at each step for clarity we have the following relavent lines [I omit register states that are not necessarily useful to see failure cause],
#101/p bpf_get_stack return R0 within range FAIL Failed to load prog 'Success'! [..] 14: (85) call bpf_get_stack#67 R0_w=map_value(id=0,off=0,ks=8,vs=48,imm=0) R3_w=inv48 15: R0=inv(id=0,smax_value=48,var32_off=(0x0; 0xffffffff)) 15: (b7) r1 = 0 16: R0=inv(id=0,smax_value=48,var32_off=(0x0; 0xffffffff)) R1_w=inv0 16: (bf) r8 = r0 17: R0=inv(id=0,smax_value=48,var32_off=(0x0; 0xffffffff)) R1_w=inv0 R8_w=inv(id=0,smax_value=48,var32_off=(0x0; 0xffffffff)) 17: (67) r8 <<= 32 18: R0=inv(id=0,smax_value=48,var32_off=(0x0; 0xffffffff)) R1_w=inv0 R8_w=inv(id=0,smax_value=9223372032559808512, umax_value=18446744069414584320, var_off=(0x0; 0xffffffff00000000), s32_min_value=0, s32_max_value=0, u32_max_value=0, var32_off=(0x0; 0x0)) 18: (c7) r8 s>>= 32 19 R0=inv(id=0,smax_value=48,var32_off=(0x0; 0xffffffff)) R1_w=inv0 R8_w=inv(id=0,smin_value=-2147483648, smax_value=2147483647, var32_off=(0x0; 0xffffffff)) 19: (cd) if r1 s< r8 goto pc+16 R0=inv(id=0,smax_value=48,var32_off=(0x0; 0xffffffff)) R1_w=inv0 R8_w=inv(id=0,smin_value=-2147483648, smax_value=0, var32_off=(0x0; 0xffffffff)) 20: R0=inv(id=0,smax_value=48,var32_off=(0x0; 0xffffffff)) R1_w=inv0 R8_w=inv(id=0,smin_value=-2147483648, smax_value=0, R9=inv48 20: (1f) r9 -= r8 21: (bf) r2 = r7 22: R2_w=map_value(id=0,off=0,ks=8,vs=48,imm=0) 22: (0f) r2 += r8 value -2147483648 makes map_value pointer be out of bounds
After call bpf_get_stack() on line 14 and some moves we have at line 16 an r8 bound with max_value 48 but an unknown min value. This is to be expected bpf_get_stack call can only return a max of the input size but is free to return any negative error in the 32-bit register space. The C helper is returning an int so will use lower 32-bits.
Lines 17 and 18 clear the top 32 bits with a left/right shift but use ARSH so we still have worst case min bound before line 19 of -2147483648. At this point the signed check 'r1 s< r8' meant to protect the addition on line 22 where dst reg is a map_value pointer may very well return true with a large negative number. Then the final line 22 will detect this as an invalid operation and fail the program. What we want to do is proceed only if r8 is positive non-error. So change 'r1 s< r8' to 'r1 s> r8' so that we jump if r8 is negative.
Next we will throw an error because we access past the end of the map value. The map value size is 48 and sizeof(struct test_val) is 48 so we walk off the end of the map value on the second call to get bpf_get_stack(). Fix this by changing sizeof(struct test_val) to 24 by using 'sizeof(struct test_val) / 2'. After this everything passes as expected.
Signed-off-by: John Fastabend john.fastabend@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/158560426019.10843.3285429543232025187.stgit@joh... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org [OP: backport to 4.19] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- tools/testing/selftests/bpf/test_verifier.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index a34552aadc129..da985a5e7cc56 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -12253,17 +12253,17 @@ static struct bpf_test tests[] = { BPF_FUNC_map_lookup_elem), BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 28), BPF_MOV64_REG(BPF_REG_7, BPF_REG_0), - BPF_MOV64_IMM(BPF_REG_9, sizeof(struct test_val)), + BPF_MOV64_IMM(BPF_REG_9, sizeof(struct test_val)/2), BPF_MOV64_REG(BPF_REG_1, BPF_REG_6), BPF_MOV64_REG(BPF_REG_2, BPF_REG_7), - BPF_MOV64_IMM(BPF_REG_3, sizeof(struct test_val)), + BPF_MOV64_IMM(BPF_REG_3, sizeof(struct test_val)/2), BPF_MOV64_IMM(BPF_REG_4, 256), BPF_EMIT_CALL(BPF_FUNC_get_stack), BPF_MOV64_IMM(BPF_REG_1, 0), BPF_MOV64_REG(BPF_REG_8, BPF_REG_0), BPF_ALU64_IMM(BPF_LSH, BPF_REG_8, 32), BPF_ALU64_IMM(BPF_ARSH, BPF_REG_8, 32), - BPF_JMP_REG(BPF_JSLT, BPF_REG_1, BPF_REG_8, 16), + BPF_JMP_REG(BPF_JSGT, BPF_REG_1, BPF_REG_8, 16), BPF_ALU64_REG(BPF_SUB, BPF_REG_9, BPF_REG_8), BPF_MOV64_REG(BPF_REG_2, BPF_REG_7), BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_8), @@ -12273,7 +12273,7 @@ static struct bpf_test tests[] = { BPF_MOV64_REG(BPF_REG_3, BPF_REG_2), BPF_ALU64_REG(BPF_ADD, BPF_REG_3, BPF_REG_1), BPF_MOV64_REG(BPF_REG_1, BPF_REG_7), - BPF_MOV64_IMM(BPF_REG_5, sizeof(struct test_val)), + BPF_MOV64_IMM(BPF_REG_5, sizeof(struct test_val)/2), BPF_ALU64_REG(BPF_ADD, BPF_REG_1, BPF_REG_5), BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_1, 4), BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
From: Daniel Borkmann daniel@iogearbox.net
stable inclusion from linux-4.19.193 commit d1e281d6cb8841122c4677b47fcebdc6f410bd74
--------------------------------
[ no upstream commit ]
Switch the comparison, so that is_branch_taken() will recognize that below branch is never taken:
[...] 17: [...] R1_w=inv0 [...] R8_w=inv(id=0,smin_value=-2147483648,smax_value=-1,umin_value=18446744071562067968,var_off=(0xffffffff80000000; 0x7fffffff)) [...] 17: (67) r8 <<= 32 18: [...] R8_w=inv(id=0,smax_value=-4294967296,umin_value=9223372036854775808,umax_value=18446744069414584320,var_off=(0x8000000000000000; 0x7fffffff00000000)) [...] 18: (c7) r8 s>>= 32 19: [...] R8_w=inv(id=0,smin_value=-2147483648,smax_value=-1,umin_value=18446744071562067968,var_off=(0xffffffff80000000; 0x7fffffff)) [...] 19: (6d) if r1 s> r8 goto pc+16 [...] R1_w=inv0 [...] R8_w=inv(id=0,smin_value=-2147483648,smax_value=-1,umin_value=18446744071562067968,var_off=(0xffffffff80000000; 0x7fffffff)) [...] [...]
Currently we check for is_branch_taken() only if either K is source, or source is a scalar value that is const. For upstream it would be good to extend this properly to check whether dst is const and src not.
For the sake of the test_verifier, it is probably not needed here:
# ./test_verifier 101 #101/p bpf_get_stack return R0 within range OK Summary: 1 PASSED, 0 SKIPPED, 0 FAILED
I haven't seen this issue in test_progs* though, they are passing fine:
# ./test_progs-no_alu32 -t get_stack Switching to flavor 'no_alu32' subdirectory... #20 get_stack_raw_tp:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
# ./test_progs -t get_stack #20 get_stack_raw_tp:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Alexei Starovoitov ast@kernel.org Acked-by: John Fastabend john.fastabend@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org [OP: backport to 4.19] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- tools/testing/selftests/bpf/test_verifier.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index da985a5e7cc56..662d6acaaab0a 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -12263,7 +12263,7 @@ static struct bpf_test tests[] = { BPF_MOV64_REG(BPF_REG_8, BPF_REG_0), BPF_ALU64_IMM(BPF_LSH, BPF_REG_8, 32), BPF_ALU64_IMM(BPF_ARSH, BPF_REG_8, 32), - BPF_JMP_REG(BPF_JSGT, BPF_REG_1, BPF_REG_8, 16), + BPF_JMP_REG(BPF_JSLT, BPF_REG_8, BPF_REG_1, 16), BPF_ALU64_REG(BPF_SUB, BPF_REG_9, BPF_REG_8), BPF_MOV64_REG(BPF_REG_2, BPF_REG_7), BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_8),
From: Daniel Borkmann daniel@iogearbox.net
stable inclusion from linux-4.19.193 commit 138b0ec1064c8f154a32297458e562591a94773f
--------------------------------
commit d7a5091351756d0ae8e63134313c455624e36a13 upstream
Update various selftest error messages:
* The 'Rx tried to sub from different maps, paths, or prohibited types' is reworked into more specific/differentiated error messages for better guidance.
* The change into 'value -4294967168 makes map_value pointer be out of bounds' is due to moving the mixed bounds check into the speculation handling and thus occuring slightly later than above mentioned sanity check.
* The change into 'math between map_value pointer and register with unbounded min value' is similarly due to register sanity check coming before the mixed bounds check.
* The case of 'map access: known scalar += value_ptr from different maps' now loads fine given masks are the same from the different paths (despite max map value size being different).
Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: John Fastabend john.fastabend@gmail.com Acked-by: Alexei Starovoitov ast@kernel.org [OP: 4.19 backport, account for split test_verifier and different / missing tests] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- tools/testing/selftests/bpf/test_verifier.c | 35 +++++++-------------- 1 file changed, 12 insertions(+), 23 deletions(-)
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index 662d6acaaab0a..e1e4b6ab83f74 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -2873,7 +2873,7 @@ static struct bpf_test tests[] = { BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0, -8), BPF_EXIT_INSN(), }, - .errstr_unpriv = "R1 tried to add from different maps, paths, or prohibited types", + .errstr_unpriv = "R1 stack pointer arithmetic goes out of range", .result_unpriv = REJECT, .result = ACCEPT, }, @@ -7501,7 +7501,6 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", - .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7526,7 +7525,6 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", - .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7553,7 +7551,6 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", - .errstr_unpriv = "R8 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7579,7 +7576,6 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", - .errstr_unpriv = "R8 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7628,7 +7624,6 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", - .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7700,7 +7695,6 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", - .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7752,7 +7746,6 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", - .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7780,7 +7773,6 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", - .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7807,7 +7799,6 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", - .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7837,7 +7828,6 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", - .errstr_unpriv = "R7 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7868,7 +7858,6 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 4 }, .errstr = "unbounded min value", - .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, }, { @@ -7897,7 +7886,6 @@ static struct bpf_test tests[] = { }, .fixup_map1 = { 3 }, .errstr = "unbounded min value", - .errstr_unpriv = "R1 has unknown scalar with mixed signed bounds", .result = REJECT, .result_unpriv = REJECT, }, @@ -9799,7 +9787,7 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1), BPF_EXIT_INSN(), }, - .errstr_unpriv = "R0 tried to sub from different maps, paths, or prohibited types", + .errstr_unpriv = "R1 has pointer with unsupported alu operation", .errstr = "R0 tried to subtract pointer from scalar", .result = REJECT, }, @@ -9814,7 +9802,7 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_1, BPF_REG_0), BPF_EXIT_INSN(), }, - .errstr_unpriv = "R1 tried to sub from different maps, paths, or prohibited types", + .errstr_unpriv = "R1 has pointer with unsupported alu operation", .result_unpriv = REJECT, .result = ACCEPT, .retval = 1, @@ -9827,22 +9815,23 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1), BPF_EXIT_INSN(), }, - .errstr_unpriv = "R0 tried to sub from different maps, paths, or prohibited types", + .errstr_unpriv = "R1 has pointer with unsupported alu operation", .errstr = "R0 tried to subtract pointer from scalar", .result = REJECT, }, { "check deducing bounds from const, 4", .insns = { + BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), BPF_MOV64_IMM(BPF_REG_0, 0), BPF_JMP_IMM(BPF_JSLE, BPF_REG_0, 0, 1), BPF_EXIT_INSN(), BPF_JMP_IMM(BPF_JSGE, BPF_REG_0, 0, 1), BPF_EXIT_INSN(), - BPF_ALU64_REG(BPF_SUB, BPF_REG_1, BPF_REG_0), + BPF_ALU64_REG(BPF_SUB, BPF_REG_6, BPF_REG_0), BPF_EXIT_INSN(), }, - .errstr_unpriv = "R1 tried to sub from different maps, paths, or prohibited types", + .errstr_unpriv = "R6 has pointer with unsupported alu operation", .result_unpriv = REJECT, .result = ACCEPT, }, @@ -9854,7 +9843,7 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1), BPF_EXIT_INSN(), }, - .errstr_unpriv = "R0 tried to sub from different maps, paths, or prohibited types", + .errstr_unpriv = "R1 has pointer with unsupported alu operation", .errstr = "R0 tried to subtract pointer from scalar", .result = REJECT, }, @@ -9867,7 +9856,7 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1), BPF_EXIT_INSN(), }, - .errstr_unpriv = "R0 tried to sub from different maps, paths, or prohibited types", + .errstr_unpriv = "R1 has pointer with unsupported alu operation", .errstr = "R0 tried to subtract pointer from scalar", .result = REJECT, }, @@ -9881,7 +9870,7 @@ static struct bpf_test tests[] = { offsetof(struct __sk_buff, mark)), BPF_EXIT_INSN(), }, - .errstr_unpriv = "R1 tried to sub from different maps, paths, or prohibited types", + .errstr_unpriv = "R1 has pointer with unsupported alu operation", .errstr = "dereference of modified ctx ptr", .result = REJECT, }, @@ -9895,7 +9884,7 @@ static struct bpf_test tests[] = { offsetof(struct __sk_buff, mark)), BPF_EXIT_INSN(), }, - .errstr_unpriv = "R1 tried to add from different maps, paths, or prohibited types", + .errstr_unpriv = "R1 has pointer with unsupported alu operation", .errstr = "dereference of modified ctx ptr", .result = REJECT, }, @@ -9907,7 +9896,7 @@ static struct bpf_test tests[] = { BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1), BPF_EXIT_INSN(), }, - .errstr_unpriv = "R0 tried to sub from different maps, paths, or prohibited types", + .errstr_unpriv = "R1 has pointer with unsupported alu operation", .errstr = "R0 tried to subtract pointer from scalar", .result = REJECT, },
From: Daniel Borkmann daniel@iogearbox.net
mainline inclusion from mainline-v5.13-rc7 commit d203b0fd863a2261e5d00b97f3d060c4c2a6db71 category: bugfix bugzilla: NA CVE: CVE-2021-33624
--------------------------------
Instead of relying on current env->pass_cnt, use the seen count from the old aux data in adjust_insn_aux_data(), and expand it to the new range of patched instructions. This change is valid given we always expand 1:n with n>=1, so what applies to the old/original instruction needs to apply for the replacement as well.
Not relying on env->pass_cnt is a prerequisite for a later change where we want to avoid marking an instruction seen when verified under speculative execution path.
Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: John Fastabend john.fastabend@gmail.com Reviewed-by: Benedict Schlueter benedict.schlueter@rub.de Reviewed-by: Piotr Krysiuk piotras@gmail.com Acked-by: Alexei Starovoitov ast@kernel.org
Conflicts: kernel/bpf/verifier.c
seen of bpf_insn_aux_data is bool in kernel-4.19.
Signed-off-by: He Fengqing hefengqing@huawei.com Reviewed-by: Kuohai Xu xukuohai@huawei.com Reviewed-by: Xiu Jianfeng xiujianfeng@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- kernel/bpf/verifier.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 08772c69edb18..a218cfdbc5805 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5905,6 +5905,7 @@ static int adjust_insn_aux_data(struct bpf_verifier_env *env, u32 prog_len, u32 off, u32 cnt) { struct bpf_insn_aux_data *new_data, *old_data = env->insn_aux_data; + bool old_seen = old_data[off].seen; int i;
if (cnt == 1) @@ -5916,8 +5917,10 @@ static int adjust_insn_aux_data(struct bpf_verifier_env *env, u32 prog_len, memcpy(new_data, old_data, sizeof(struct bpf_insn_aux_data) * off); memcpy(new_data + off + cnt - 1, old_data + off, sizeof(struct bpf_insn_aux_data) * (prog_len - off - cnt + 1)); - for (i = off; i < off + cnt - 1; i++) - new_data[i].seen = true; + for (i = off; i < off + cnt - 1; i++) { + /* Expand insni[off]'s seen count to the patched range. */ + new_data[i].seen = old_seen; + } env->insn_aux_data = new_data; vfree(old_data); return 0;
From: Daniel Borkmann daniel@iogearbox.net
mainline inclusion from mainline-v5.13-rc7 commit fe9a5ca7e370e613a9a75a13008a3845ea759d6e category: bugfix bugzilla: NA CVE: CVE-2021-33624
--------------------------------
... in such circumstances, we do not want to mark the instruction as seen given the goal is still to jmp-1 rewrite/sanitize dead code, if it is not reachable from the non-speculative path verification. We do however want to verify it for safety regardless.
With the patch as-is all the insns that have been marked as seen before the patch will also be marked as seen after the patch (just with a potentially different non-zero count). An upcoming patch will also verify paths that are unreachable in the non-speculative domain, hence this extension is needed.
Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: John Fastabend john.fastabend@gmail.com Reviewed-by: Benedict Schlueter benedict.schlueter@rub.de Reviewed-by: Piotr Krysiuk piotras@gmail.com Acked-by: Alexei Starovoitov ast@kernel.org
Conflicts: kernel/bpf/verifier.c
pass_cnt is not introduced in kernel-4.19.
Signed-off-by: He Fengqing hefengqing@huawei.com Reviewed-by: Kuohai Xu xukuohai@huawei.com Reviewed-by: Xiu Jianfeng xiujianfeng@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- kernel/bpf/verifier.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index a218cfdbc5805..bc62a9d395359 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2932,6 +2932,19 @@ static int sanitize_ptr_alu(struct bpf_verifier_env *env, return !ret ? REASON_STACK : 0; }
+static void sanitize_mark_insn_seen(struct bpf_verifier_env *env) +{ + struct bpf_verifier_state *vstate = env->cur_state; + + /* If we simulate paths under speculation, we don't update the + * insn as 'seen' such that when we verify unreachable paths in + * the non-speculative domain, sanitize_dead_code() can still + * rewrite/sanitize them. + */ + if (!vstate->speculative) + env->insn_aux_data[env->insn_idx].seen = true; +} + static int sanitize_err(struct bpf_verifier_env *env, const struct bpf_insn *insn, int reason, const struct bpf_reg_state *off_reg, @@ -5466,7 +5479,7 @@ static int do_check(struct bpf_verifier_env *env) }
regs = cur_regs(env); - env->insn_aux_data[env->insn_idx].seen = true; + sanitize_mark_insn_seen(env);
if (class == BPF_ALU || class == BPF_ALU64) { err = check_alu_op(env, insn); @@ -5687,7 +5700,7 @@ static int do_check(struct bpf_verifier_env *env) return err;
env->insn_idx++; - env->insn_aux_data[env->insn_idx].seen = true; + sanitize_mark_insn_seen(env); } else { verbose(env, "invalid BPF_LD mode\n"); return -EINVAL;
From: Daniel Borkmann daniel@iogearbox.net
mainline inclusion from mainline-v5.13-rc7 commit 9183671af6dbf60a1219371d4ed73e23f43b49db category: bugfix bugzilla: NA CVE: CVE-2021-33624
--------------------------------
The verifier only enumerates valid control-flow paths and skips paths that are unreachable in the non-speculative domain. And so it can miss issues under speculative execution on mispredicted branches.
For example, a type confusion has been demonstrated with the following crafted program:
// r0 = pointer to a map array entry // r6 = pointer to readable stack slot // r9 = scalar controlled by attacker 1: r0 = *(u64 *)(r0) // cache miss 2: if r0 != 0x0 goto line 4 3: r6 = r9 4: if r0 != 0x1 goto line 6 5: r9 = *(u8 *)(r6) 6: // leak r9
Since line 3 runs iff r0 == 0 and line 5 runs iff r0 == 1, the verifier concludes that the pointer dereference on line 5 is safe. But: if the attacker trains both the branches to fall-through, such that the following is speculatively executed ...
r6 = r9 r9 = *(u8 *)(r6) // leak r9
... then the program will dereference an attacker-controlled value and could leak its content under speculative execution via side-channel. This requires to mistrain the branch predictor, which can be rather tricky, because the branches are mutually exclusive. However such training can be done at congruent addresses in user space using different branches that are not mutually exclusive. That is, by training branches in user space ...
A: if r0 != 0x0 goto line C B: ... C: if r0 != 0x0 goto line D D: ...
... such that addresses A and C collide to the same CPU branch prediction entries in the PHT (pattern history table) as those of the BPF program's lines 2 and 4, respectively. A non-privileged attacker could simply brute force such collisions in the PHT until observing the attack succeeding.
Alternative methods to mistrain the branch predictor are also possible that avoid brute forcing the collisions in the PHT. A reliable attack has been demonstrated, for example, using the following crafted program:
// r0 = pointer to a [control] map array entry // r7 = *(u64 *)(r0 + 0), training/attack phase // r8 = *(u64 *)(r0 + 8), oob address // [...] // r0 = pointer to a [data] map array entry 1: if r7 == 0x3 goto line 3 2: r8 = r0 // crafted sequence of conditional jumps to separate the conditional // branch in line 193 from the current execution flow 3: if r0 != 0x0 goto line 5 4: if r0 == 0x0 goto exit 5: if r0 != 0x0 goto line 7 6: if r0 == 0x0 goto exit [...] 187: if r0 != 0x0 goto line 189 188: if r0 == 0x0 goto exit // load any slowly-loaded value (due to cache miss in phase 3) ... 189: r3 = *(u64 *)(r0 + 0x1200) // ... and turn it into known zero for verifier, while preserving slowly- // loaded dependency when executing: 190: r3 &= 1 191: r3 &= 2 // speculatively bypassed phase dependency 192: r7 += r3 193: if r7 == 0x3 goto exit 194: r4 = *(u8 *)(r8 + 0) // leak r4
As can be seen, in training phase (phase != 0x3), the condition in line 1 turns into false and therefore r8 with the oob address is overridden with the valid map value address, which in line 194 we can read out without issues. However, in attack phase, line 2 is skipped, and due to the cache miss in line 189 where the map value is (zeroed and later) added to the phase register, the condition in line 193 takes the fall-through path due to prior branch predictor training, where under speculation, it'll load the byte at oob address r8 (unknown scalar type at that point) which could then be leaked via side-channel.
One way to mitigate these is to 'branch off' an unreachable path, meaning, the current verification path keeps following the is_branch_taken() path and we push the other branch to the verification stack. Given this is unreachable from the non-speculative domain, this branch's vstate is explicitly marked as speculative. This is needed for two reasons: i) if this path is solely seen from speculative execution, then we later on still want the dead code elimination to kick in in order to sanitize these instructions with jmp-1s, and ii) to ensure that paths walked in the non-speculative domain are not pruned from earlier walks of paths walked in the speculative domain. Additionally, for robustness, we mark the registers which have been part of the conditional as unknown in the speculative path given there should be no assumptions made on their content.
The fix in here mitigates type confusion attacks described earlier due to i) all code paths in the BPF program being explored and ii) existing verifier logic already ensuring that given memory access instruction references one specific data structure.
An alternative to this fix that has also been looked at in this scope was to mark aux->alu_state at the jump instruction with a BPF_JMP_TAKEN state as well as direction encoding (always-goto, always-fallthrough, unknown), such that mixing of different always-* directions themselves as well as mixing of always-* with unknown directions would cause a program rejection by the verifier, e.g. programs with constructs like 'if ([...]) { x = 0; } else { x = 1; }' with subsequent 'if (x == 1) { [...] }'. For unprivileged, this would result in only single direction always-* taken paths, and unknown taken paths being allowed, such that the former could be patched from a conditional jump to an unconditional jump (ja). Compared to this approach here, it would have two downsides: i) valid programs that otherwise are not performing any pointer arithmetic, etc, would potentially be rejected/broken, and ii) we are required to turn off path pruning for unprivileged, where both can be avoided in this work through pushing the invalid branch to the verification stack.
The issue was originally discovered by Adam and Ofek, and later independently discovered and reported as a result of Benedict and Piotr's research work.
Fixes: b2157399cc98 ("bpf: prevent out-of-bounds speculation") Reported-by: Adam Morrison mad@cs.tau.ac.il Reported-by: Ofek Kirzner ofekkir@gmail.com Reported-by: Benedict Schlueter benedict.schlueter@rub.de Reported-by: Piotr Krysiuk piotras@gmail.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: John Fastabend john.fastabend@gmail.com Reviewed-by: Benedict Schlueter benedict.schlueter@rub.de Reviewed-by: Piotr Krysiuk piotras@gmail.com Acked-by: Alexei Starovoitov ast@kernel.org
onflicts: kernel/bpf/verifier.c [yyl: bypass_spec_v1 is not introduced in kernel-4.19, use allow_ptr_leaks instead]
Signed-off-by: Yang Yingliang yangyingliang@huawei.com Signed-off-by: He Fengqinghefengqing@huawei.com Reviewed-by: Kuohai Xu xukuohai@huawei.com Reviewed-by: Xiu Jianfeng xiujianfeng@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- kernel/bpf/verifier.c | 46 +++++++++++++++++++++++++++++++++++++++---- 1 file changed, 42 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index bc62a9d395359..650cec781f5a8 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2843,6 +2843,27 @@ struct bpf_sanitize_info { bool mask_to_left; };
+static struct bpf_verifier_state * +sanitize_speculative_path(struct bpf_verifier_env *env, + const struct bpf_insn *insn, + u32 next_idx, u32 curr_idx) +{ + struct bpf_verifier_state *branch; + struct bpf_reg_state *regs; + + branch = push_stack(env, next_idx, curr_idx, true); + if (branch && insn) { + regs = branch->frame[branch->curframe]->regs; + if (BPF_SRC(insn->code) == BPF_K) { + mark_reg_unknown(env, regs, insn->dst_reg); + } else if (BPF_SRC(insn->code) == BPF_X) { + mark_reg_unknown(env, regs, insn->dst_reg); + mark_reg_unknown(env, regs, insn->src_reg); + } + } + return branch; +} + static int sanitize_ptr_alu(struct bpf_verifier_env *env, struct bpf_insn *insn, const struct bpf_reg_state *ptr_reg, @@ -2926,7 +2947,8 @@ static int sanitize_ptr_alu(struct bpf_verifier_env *env, tmp = *dst_reg; *dst_reg = *ptr_reg; } - ret = push_stack(env, env->insn_idx + 1, env->insn_idx, true); + ret = sanitize_speculative_path(env, NULL, env->insn_idx + 1, + env->insn_idx); if (!ptr_is_dst_reg && ret) *dst_reg = tmp; return !ret ? REASON_STACK : 0; @@ -4478,14 +4500,30 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, tnum_is_const(src_reg->var_off)) pred = is_branch_taken(dst_reg, src_reg->var_off.value, opcode, is_jmp32); + if (pred == 1) { - /* only follow the goto, ignore fall-through */ + /* Only follow the goto, ignore fall-through. If needed, push + * the fall-through branch for simulation under speculative + * execution. + */ + if (!env->allow_ptr_leaks && + !sanitize_speculative_path(env, insn, *insn_idx + 1, + *insn_idx)) + return -EFAULT; + *insn_idx += insn->off; return 0; } else if (pred == 0) { - /* only follow fall-through branch, since - * that's where the program will go + /* Only follow the fall-through branch, since that's where the + * program will go. If needed, push the goto branch for + * simulation under speculative execution. */ + if (!env->allow_ptr_leaks && + !sanitize_speculative_path(env, insn, + *insn_idx + insn->off + 1, + *insn_idx)) + return -EFAULT; + return 0; }
-
Yang Yingliang