From: Peter Zijlstra <peterz@infradead.org> mainline inclusion from mainline-v6.8-rc1 commit 4f9087f16651aca4a5f32da840a53f6660f0579a category: feature bugzilla: https://atomgit.com/openeuler/kernel/issues/8335 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... ---------------------------------------------------------------------- The current BPF call convention is __nocfi, except when it calls !JIT things, then it calls regular C functions. It so happens that with FineIBT the __nocfi and C calling conventions are incompatible. Specifically __nocfi will call at func+0, while FineIBT will have endbr-poison there, which is not a valid indirect target. Causing #CP. Notably this only triggers on IBT enabled hardware, which is probably why this hasn't been reported (also, most people will have JIT on anyway). Implement proper CFI prologues for the BPF JIT codegen and drop __nocfi for x86. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20231215092707.345270396@infradead.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> Conflicts: arch/x86/net/bpf_jit_comp.c include/linux/bpf.h kernel/bpf/core.c [Fix conflict because of kabi and cev patches db775a8ebf140, and pre-patches fd5d27b70188 is not existed.] Signed-off-by: Luo Gengkun <luogengkun2@huawei.com> --- arch/x86/include/asm/cfi.h | 110 ++++++++++++++++++++++++++++++++++ arch/x86/kernel/alternative.c | 47 ++++++++++++--- arch/x86/net/bpf_jit_comp.c | 82 +++++++++++++++++++++++-- include/linux/bpf.h | 13 +++- include/linux/cfi.h | 7 +++ kernel/bpf/core.c | 25 ++++++++ 6 files changed, 270 insertions(+), 14 deletions(-) diff --git a/arch/x86/include/asm/cfi.h b/arch/x86/include/asm/cfi.h index 2a494643089d..7a7b0b823a98 100644 --- a/arch/x86/include/asm/cfi.h +++ b/arch/x86/include/asm/cfi.h @@ -9,15 +9,125 @@ */ #include <linux/bug.h> +/* + * An overview of the various calling conventions... + * + * Traditional: + * + * foo: + * ... code here ... + * ret + * + * direct caller: + * call foo + * + * indirect caller: + * lea foo(%rip), %r11 + * ... + * call *%r11 + * + * + * IBT: + * + * foo: + * endbr64 + * ... code here ... + * ret + * + * direct caller: + * call foo / call foo+4 + * + * indirect caller: + * lea foo(%rip), %r11 + * ... + * call *%r11 + * + * + * kCFI: + * + * __cfi_foo: + * movl $0x12345678, %eax + * # 11 nops when CONFIG_CALL_PADDING + * foo: + * endbr64 # when IBT + * ... code here ... + * ret + * + * direct call: + * call foo # / call foo+4 when IBT + * + * indirect call: + * lea foo(%rip), %r11 + * ... + * movl $(-0x12345678), %r10d + * addl -4(%r11), %r10d # -15 when CONFIG_CALL_PADDING + * jz 1f + * ud2 + * 1:call *%r11 + * + * + * FineIBT (builds as kCFI + CALL_PADDING + IBT + RETPOLINE and runtime patches into): + * + * __cfi_foo: + * endbr64 + * subl 0x12345678, %r10d + * jz foo + * ud2 + * nop + * foo: + * osp nop3 # was endbr64 + * ... code here ... + * ret + * + * direct caller: + * call foo / call foo+4 + * + * indirect caller: + * lea foo(%rip), %r11 + * ... + * movl $0x12345678, %r10d + * subl $16, %r11 + * nop4 + * call *%r11 + * + */ +enum cfi_mode { + CFI_DEFAULT, /* FineIBT if hardware has IBT, otherwise kCFI */ + CFI_OFF, /* Taditional / IBT depending on .config */ + CFI_KCFI, /* Optionally CALL_PADDING, IBT, RETPOLINE */ + CFI_FINEIBT, /* see arch/x86/kernel/alternative.c */ +}; + +extern enum cfi_mode cfi_mode; + struct pt_regs; #ifdef CONFIG_CFI_CLANG enum bug_trap_type handle_cfi_failure(struct pt_regs *regs); +#define __bpfcall +extern u32 cfi_bpf_hash; + +static inline int cfi_get_offset(void) +{ + switch (cfi_mode) { + case CFI_FINEIBT: + return 16; + case CFI_KCFI: + if (IS_ENABLED(CONFIG_CALL_PADDING)) + return 16; + return 5; + default: + return 0; + } +} +#define cfi_get_offset cfi_get_offset + #else static inline enum bug_trap_type handle_cfi_failure(struct pt_regs *regs) { return BUG_TRAP_TYPE_NONE; } +#define cfi_bpf_hash 0U #endif /* CONFIG_CFI_CLANG */ #endif /* _ASM_X86_CFI_H */ diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index aae7456ece07..811f4a1f0fdf 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -30,6 +30,7 @@ #include <asm/fixmap.h> #include <asm/paravirt.h> #include <asm/asm-prototypes.h> +#include <asm/cfi.h> int __read_mostly alternatives_patched; @@ -842,15 +843,43 @@ void __init_or_module apply_seal_endbr(s32 *start, s32 *end) { } #endif /* CONFIG_X86_KERNEL_IBT */ #ifdef CONFIG_FINEIBT +#define __CFI_DEFAULT CFI_DEFAULT +#elif defined(CONFIG_CFI_CLANG) +#define __CFI_DEFAULT CFI_KCFI +#else +#define __CFI_DEFAULT CFI_OFF +#endif -enum cfi_mode { - CFI_DEFAULT, - CFI_OFF, - CFI_KCFI, - CFI_FINEIBT, -}; +enum cfi_mode cfi_mode __ro_after_init = __CFI_DEFAULT; + +#ifdef CONFIG_CFI_CLANG +struct bpf_insn; + +/* Must match bpf_func_t / DEFINE_BPF_PROG_RUN() */ +extern unsigned int __bpf_prog_runX(const void *ctx, + const struct bpf_insn *insn); + +/* + * Force a reference to the external symbol so the compiler generates + * __kcfi_typid. + */ +__ADDRESSABLE(__bpf_prog_runX); + +/* u32 __ro_after_init cfi_bpf_hash = __kcfi_typeid___bpf_prog_runX; */ +asm ( +" .pushsection .data..ro_after_init,\"aw\",@progbits \n" +" .type cfi_bpf_hash,@object \n" +" .globl cfi_bpf_hash \n" +" .p2align 2, 0x0 \n" +"cfi_bpf_hash: \n" +" .long __kcfi_typeid___bpf_prog_runX \n" +" .size cfi_bpf_hash, 4 \n" +" .popsection \n" +); +#endif + +#ifdef CONFIG_FINEIBT -static enum cfi_mode cfi_mode __ro_after_init = CFI_DEFAULT; static bool cfi_rand __ro_after_init = true; static u32 cfi_seed __ro_after_init; @@ -1159,8 +1188,10 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline, goto err; if (cfi_rand) { - if (builtin) + if (builtin) { cfi_seed = get_random_u32(); + cfi_bpf_hash = cfi_rehash(cfi_bpf_hash); + } ret = cfi_rand_preamble(start_cfi, end_cfi); if (ret) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 724636778ea5..8256bf41f4d0 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -16,6 +16,7 @@ #include <asm/set_memory.h> #include <asm/nospec-branch.h> #include <asm/text-patching.h> +#include <asm/cfi.h> static u8 *emit_code(u8 *ptr, u32 bytes, unsigned int len) { @@ -48,9 +49,11 @@ static u8 *emit_code(u8 *ptr, u32 bytes, unsigned int len) do { EMIT4(b1, b2, b3, b4); EMIT(off, 4); } while (0) #ifdef CONFIG_X86_KERNEL_IBT -#define EMIT_ENDBR() EMIT(gen_endbr(), 4) +#define EMIT_ENDBR() EMIT(gen_endbr(), 4) +#define EMIT_ENDBR_POISON() EMIT(gen_endbr_poison(), 4) #else #define EMIT_ENDBR() +#define EMIT_ENDBR_POISON() #endif static bool is_imm8(int value) @@ -335,6 +338,69 @@ static void pop_callee_regs(u8 **pprog, bool *callee_regs_used) *pprog = prog; } +/* + * Emit the various CFI preambles, see asm/cfi.h and the comments about FineIBT + * in arch/x86/kernel/alternative.c + */ + +static void emit_fineibt(u8 **pprog) +{ + u8 *prog = *pprog; + + EMIT_ENDBR(); + EMIT3_off32(0x41, 0x81, 0xea, cfi_bpf_hash); /* subl $hash, %r10d */ + EMIT2(0x74, 0x07); /* jz.d8 +7 */ + EMIT2(0x0f, 0x0b); /* ud2 */ + EMIT1(0x90); /* nop */ + EMIT_ENDBR_POISON(); + + *pprog = prog; +} + +static void emit_kcfi(u8 **pprog) +{ + u8 *prog = *pprog; + + EMIT1_off32(0xb8, cfi_bpf_hash); /* movl $hash, %eax */ +#ifdef CONFIG_CALL_PADDING + EMIT1(0x90); + EMIT1(0x90); + EMIT1(0x90); + EMIT1(0x90); + EMIT1(0x90); + EMIT1(0x90); + EMIT1(0x90); + EMIT1(0x90); + EMIT1(0x90); + EMIT1(0x90); + EMIT1(0x90); +#endif + EMIT_ENDBR(); + + *pprog = prog; +} + +static void emit_cfi(u8 **pprog) +{ + u8 *prog = *pprog; + + switch (cfi_mode) { + case CFI_FINEIBT: + emit_fineibt(&prog); + break; + + case CFI_KCFI: + emit_kcfi(&prog); + break; + + default: + EMIT_ENDBR(); + break; + } + + *pprog = prog; +} + /* * Emit x86-64 prologue code for BPF program. * bpf_tail_call helper will skip the first X86_TAIL_CALL_OFFSET bytes @@ -345,10 +411,10 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf, { u8 *prog = *pprog; + emit_cfi(&prog); /* BPF trampoline can be made to work without these nops, * but let's waste 5 bytes for now and optimize later */ - EMIT_ENDBR(); memcpy(prog, x86_nops[5], X86_PATCH_SIZE); prog += X86_PATCH_SIZE; if (!ebpf_from_cbpf) { @@ -2986,9 +3052,16 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) jit_data->header = header; jit_data->rw_header = rw_header; } - prog->bpf_func = (void *)image; + /* + * ctx.prog_offset is used when CFI preambles put code *before* + * the function. See emit_cfi(). For FineIBT specifically this code + * can also be executed and bpf_prog_kallsyms_add() will + * generate an additional symbol to cover this, hence also + * decrement proglen. + */ + prog->bpf_func = (void *)image + cfi_get_offset(); prog->jited = 1; - prog->jited_len = proglen; + prog->jited_len = proglen - cfi_get_offset(); } else { prog = orig_prog; } @@ -3043,6 +3116,7 @@ void bpf_jit_free(struct bpf_prog *prog) kvfree(jit_data->addrs); kfree(jit_data); } + prog->bpf_func = (void *)prog->bpf_func - cfi_get_offset(); hdr = bpf_jit_binary_pack_hdr(prog); bpf_jit_binary_pack_free(hdr, NULL); WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(prog)); diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 4cee60abb1bb..f3f0da996780 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -30,6 +30,7 @@ #include <linux/static_call.h> #include <linux/memcontrol.h> #include <linux/kabi.h> +#include <linux/cfi.h> struct bpf_verifier_env; struct bpf_verifier_log; @@ -1278,7 +1279,12 @@ struct bpf_dispatcher { KABI_RESERVE(4) }; -static __always_inline __nocfi unsigned int bpf_dispatcher_nop_func( +#ifndef __bpfcall +#define __bpfcall __nocfi +#endif + +static __always_inline __bpfcall unsigned int bpf_dispatcher_nop_func( + const void *ctx, const struct bpf_insn *insnsi, bpf_func_t bpf_func) @@ -1372,7 +1378,7 @@ int arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_func #define DEFINE_BPF_DISPATCHER(name) \ __BPF_DISPATCHER_SC(name); \ - noinline __nocfi unsigned int bpf_dispatcher_##name##_func( \ + noinline __bpfcall unsigned int bpf_dispatcher_##name##_func( \ const void *ctx, \ const struct bpf_insn *insnsi, \ bpf_func_t bpf_func) \ @@ -1523,6 +1529,9 @@ struct bpf_prog_aux { struct bpf_kfunc_desc_tab *kfunc_tab; struct bpf_kfunc_btf_tab *kfunc_btf_tab; u32 size_poke_tab; +#ifdef CONFIG_FINEIBT + struct bpf_ksym ksym_prefix; +#endif struct bpf_ksym ksym; const struct bpf_prog_ops *ops; struct bpf_map **used_maps; diff --git a/include/linux/cfi.h b/include/linux/cfi.h index 2309d74e77e6..1ed2d96c0cfc 100644 --- a/include/linux/cfi.h +++ b/include/linux/cfi.h @@ -11,6 +11,13 @@ #include <linux/module.h> #include <asm/cfi.h> +#ifndef cfi_get_offset +static inline int cfi_get_offset(void) +{ + return 0; +} +#endif + #ifdef CONFIG_CFI_CLANG enum bug_trap_type report_cfi_failure(struct pt_regs *regs, unsigned long addr, unsigned long *target, u32 type); diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 4dca8a24adbb..b6aea05f0c19 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -121,6 +121,9 @@ struct bpf_prog *bpf_prog_alloc_no_stats(unsigned int size, gfp_t gfp_extra_flag #endif INIT_LIST_HEAD_RCU(&fp->aux->ksym.lnode); +#ifdef CONFIG_FINEIBT + INIT_LIST_HEAD_RCU(&fp->aux->ksym_prefix.lnode); +#endif mutex_init(&fp->aux->used_maps_mutex); mutex_init(&fp->aux->ext_mutex); mutex_init(&fp->aux->dst_mutex); @@ -692,6 +695,23 @@ void bpf_prog_kallsyms_add(struct bpf_prog *fp) fp->aux->ksym.prog = true; bpf_ksym_add(&fp->aux->ksym); + +#ifdef CONFIG_FINEIBT + /* + * When FineIBT, code in the __cfi_foo() symbols can get executed + * and hence unwinder needs help. + */ + if (cfi_mode != CFI_FINEIBT) + return; + + snprintf(fp->aux->ksym_prefix.name, KSYM_NAME_LEN, + "__cfi_%s", fp->aux->ksym.name); + + fp->aux->ksym_prefix.start = (unsigned long) fp->bpf_func - 16; + fp->aux->ksym_prefix.end = (unsigned long) fp->bpf_func; + + bpf_ksym_add(&fp->aux->ksym_prefix); +#endif } void bpf_prog_kallsyms_del(struct bpf_prog *fp) @@ -700,6 +720,11 @@ void bpf_prog_kallsyms_del(struct bpf_prog *fp) return; bpf_ksym_del(&fp->aux->ksym); +#ifdef CONFIG_FINEIBT + if (cfi_mode != CFI_FINEIBT) + return; + bpf_ksym_del(&fp->aux->ksym_prefix); +#endif } static struct bpf_ksym *bpf_ksym_find(unsigned long addr) -- 2.34.1