[PATCH OLK-6.6 0/3] mainline patch for bpf
Daniel Borkmann (1): bpf: Fix incorrect pruning due to atomic fetch precision tracking Qi Tang (1): bpf: reject direct access to nullable PTR_TO_BUF pointers Varun R Mallya (1): bpf: Reject sleepable kprobe_multi programs at attach time kernel/bpf/verifier.c | 28 ++++++++++++++++++++++++---- kernel/trace/bpf_trace.c | 4 ++++ 2 files changed, 28 insertions(+), 4 deletions(-) -- 2.34.1
From: Varun R Mallya <varunrmallya@gmail.com> mainline inclusion from mainline-v7.0-rc7 commit eb7024bfcc5f68ed11ed9dd4891a3073c15f04a8 category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/9004 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- kprobe.multi programs run in atomic/RCU context and cannot sleep. However, bpf_kprobe_multi_link_attach() did not validate whether the program being attached had the sleepable flag set, allowing sleepable helpers such as bpf_copy_from_user() to be invoked from a non-sleepable context. This causes a "sleeping function called from invalid context" splat: BUG: sleeping function called from invalid context at ./include/linux/uaccess.h:169 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1787, name: sudo preempt_count: 1, expected: 0 RCU nest depth: 2, expected: 0 Fix this by rejecting sleepable programs early in bpf_kprobe_multi_link_attach(), before any further processing. Fixes: 0dcac2725406 ("bpf: Add multi kprobe link") Signed-off-by: Varun R Mallya <varunrmallya@gmail.com> Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Acked-by: Leon Hwang <leon.hwang@linux.dev> Acked-by: Jiri Olsa <jolsa@kernel.org> Link: https://lore.kernel.org/r/20260401191126.440683-1-varunrmallya@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Conflicts: kernel/trace/bpf_trace.c [ctx conflicts] Signed-off-by: Pu Lehui <pulehui@huawei.com> --- kernel/trace/bpf_trace.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 50556b239023..1cdb832b9be5 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2901,6 +2901,10 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr if (sizeof(u64) != sizeof(void *)) return -EOPNOTSUPP; + /* kprobe_multi is not allowed to be sleepable. */ + if (prog->sleepable) + return -EINVAL; + if (prog->expected_attach_type != BPF_TRACE_KPROBE_MULTI) return -EINVAL; -- 2.34.1
From: Qi Tang <tpluszz77@gmail.com> mainline inclusion from mainline-v7.0-rc7 commit b0db1accbc7395657c2b79db59fa9fae0d6656f3 category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/9004 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- check_mem_access() matches PTR_TO_BUF via base_type() which strips PTR_MAYBE_NULL, allowing direct dereference without a null check. Map iterator ctx->key and ctx->value are PTR_TO_BUF | PTR_MAYBE_NULL. On stop callbacks these are NULL, causing a kernel NULL dereference. Add a type_may_be_null() guard to the PTR_TO_BUF branch, matching the existing PTR_TO_BTF_ID pattern. Fixes: 20b2aff4bc15 ("bpf: Introduce MEM_RDONLY flag") Signed-off-by: Qi Tang <tpluszz77@gmail.com> Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20260402092923.38357-2-tpluszz77@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Pu Lehui <pulehui@huawei.com> --- kernel/bpf/verifier.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index e63d63ac8a36..61ba15a96e61 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6997,7 +6997,8 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn } else if (reg->type == CONST_PTR_TO_MAP) { err = check_ptr_to_map_access(env, regs, regno, off, size, t, value_regno); - } else if (base_type(reg->type) == PTR_TO_BUF) { + } else if (base_type(reg->type) == PTR_TO_BUF && + !type_may_be_null(reg->type)) { bool rdonly_mem = type_is_rdonly_mem(reg->type); u32 *max_access; -- 2.34.1
From: Daniel Borkmann <daniel@iogearbox.net> mainline inclusion from mainline-v7.0-rc7 commit 179ee84a89114b854ac2dd1d293633a7f6c8dac1 category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/9004 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- When backtrack_insn encounters a BPF_STX instruction with BPF_ATOMIC and BPF_FETCH, the src register (or r0 for BPF_CMPXCHG) also acts as a destination, thus receiving the old value from the memory location. The current backtracking logic does not account for this. It treats atomic fetch operations the same as regular stores where the src register is only an input. This leads the backtrack_insn to fail to propagate precision to the stack location, which is then not marked as precise! Later, the verifier's path pruning can incorrectly consider two states equivalent when they differ in terms of stack state. Meaning, two branches can be treated as equivalent and thus get pruned when they should not be seen as such. Fix it as follows: Extend the BPF_LDX handling in backtrack_insn to also cover atomic fetch operations via is_atomic_fetch_insn() helper. When the fetch dst register is being tracked for precision, clear it, and propagate precision over to the stack slot. For non-stack memory, the precision walk stops at the atomic instruction, same as regular BPF_LDX. This covers all fetch variants. Before: 0: (b7) r1 = 8 ; R1=8 1: (7b) *(u64 *)(r10 -8) = r1 ; R1=8 R10=fp0 fp-8=8 2: (b7) r2 = 0 ; R2=0 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) ; R2=8 R10=fp0 fp-8=mmmmmmmm 4: (bf) r3 = r10 ; R3=fp0 R10=fp0 5: (0f) r3 += r2 mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1 mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10 mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) mark_precise: frame0: regs=r2 stack= before 2: (b7) r2 = 0 6: R2=8 R3=fp8 6: (b7) r0 = 0 ; R0=0 7: (95) exit After: 0: (b7) r1 = 8 ; R1=8 1: (7b) *(u64 *)(r10 -8) = r1 ; R1=8 R10=fp0 fp-8=8 2: (b7) r2 = 0 ; R2=0 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) ; R2=8 R10=fp0 fp-8=mmmmmmmm 4: (bf) r3 = r10 ; R3=fp0 R10=fp0 5: (0f) r3 += r2 mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1 mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10 mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) mark_precise: frame0: regs= stack=-8 before 2: (b7) r2 = 0 mark_precise: frame0: regs= stack=-8 before 1: (7b) *(u64 *)(r10 -8) = r1 mark_precise: frame0: regs=r1 stack= before 0: (b7) r1 = 8 6: R2=8 R3=fp8 6: (b7) r0 = 0 ; R0=0 7: (95) exit Fixes: 5ffa25502b5a ("bpf: Add instructions for atomic_[cmp]xchg") Fixes: 5ca419f2864a ("bpf: Add BPF_FETCH field / create atomic_fetch_add instruction") Reported-by: STAR Labs SG <info@starlabs.sg> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/r/20260331222020.401848-1-daniel@iogearbox.net Signed-off-by: Alexei Starovoitov <ast@kernel.org> Conflicts: kernel/bpf/verifier.c [ctx conflicts] Signed-off-by: Pu Lehui <pulehui@huawei.com> --- kernel/bpf/verifier.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 61ba15a96e61..db9dd64dd86b 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -684,6 +684,13 @@ static void print_liveness(struct bpf_verifier_env *env, verbose(env, "D"); } +static bool is_atomic_fetch_insn(const struct bpf_insn *insn) +{ + return BPF_CLASS(insn->code) == BPF_STX && + BPF_MODE(insn->code) == BPF_ATOMIC && + (insn->imm & BPF_FETCH); +} + static int __get_spi(s32 off) { return (-off - 1) / BPF_REG_SIZE; @@ -3808,10 +3815,22 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx, * dreg still needs precision before this insn */ } - } else if (class == BPF_LDX) { - if (!bt_is_reg_set(bt, dreg)) + } else if (class == BPF_LDX || is_atomic_fetch_insn(insn)) { + u32 load_reg = dreg; + + /* + * Atomic fetch operation writes the old value into + * a register (sreg or r0) and if it was tracked for + * precision, propagate to the stack slot like we do + * in regular ldx. + */ + if (is_atomic_fetch_insn(insn)) + load_reg = insn->imm == BPF_CMPXCHG ? + BPF_REG_0 : sreg; + + if (!bt_is_reg_set(bt, load_reg)) return 0; - bt_clear_reg(bt, dreg); + bt_clear_reg(bt, load_reg); /* scalars can only be spilled into stack w/o losing precision. * Load from any other memory can be zero extended. -- 2.34.1
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