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| author | Peter Zijlstra <peterz@infradead.org> | 2021-10-30 10:47:58 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-11-11 15:09:31 +0300 |
| commit | 2105a92748e83e2e3ee6be539da959706bbb3898 (patch) | |
| tree | 04dd3c3a9a55be81189d30054b015b2587dc5968 /arch | |
| parent | debe436e77c72fcee804fb867f275e6d31aa999c (diff) | |
| download | linux-2105a92748e83e2e3ee6be539da959706bbb3898.tar.xz | |
static_call,x86: Robustify trampoline patching
Add a few signature bytes after the static call trampoline and verify
those bytes match before patching the trampoline. This avoids patching
random other JMPs (such as CFI jump-table entries) instead.
These bytes decode as:
d: 53 push %rbx
e: 43 54 rex.XB push %r12
And happen to spell "SCT".
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211030074758.GT174703@worktop.programming.kicks-ass.net
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/static_call.h | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/static_call.c | 14 |
2 files changed, 11 insertions, 4 deletions
diff --git a/arch/x86/include/asm/static_call.h b/arch/x86/include/asm/static_call.h index cbb67b6030f9..39ebe0511869 100644 --- a/arch/x86/include/asm/static_call.h +++ b/arch/x86/include/asm/static_call.h @@ -27,6 +27,7 @@ ".globl " STATIC_CALL_TRAMP_STR(name) " \n" \ STATIC_CALL_TRAMP_STR(name) ": \n" \ insns " \n" \ + ".byte 0x53, 0x43, 0x54 \n" \ ".type " STATIC_CALL_TRAMP_STR(name) ", @function \n" \ ".size " STATIC_CALL_TRAMP_STR(name) ", . - " STATIC_CALL_TRAMP_STR(name) " \n" \ ".popsection \n") diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c index ea028e736831..9c407a33a774 100644 --- a/arch/x86/kernel/static_call.c +++ b/arch/x86/kernel/static_call.c @@ -56,10 +56,15 @@ static void __ref __static_call_transform(void *insn, enum insn_type type, void text_poke_bp(insn, code, size, emulate); } -static void __static_call_validate(void *insn, bool tail) +static void __static_call_validate(void *insn, bool tail, bool tramp) { u8 opcode = *(u8 *)insn; + if (tramp && memcmp(insn+5, "SCT", 3)) { + pr_err("trampoline signature fail"); + BUG(); + } + if (tail) { if (opcode == JMP32_INSN_OPCODE || opcode == RET_INSN_OPCODE) @@ -74,7 +79,8 @@ static void __static_call_validate(void *insn, bool tail) /* * If we ever trigger this, our text is corrupt, we'll probably not live long. */ - WARN_ONCE(1, "unexpected static_call insn opcode 0x%x at %pS\n", opcode, insn); + pr_err("unexpected static_call insn opcode 0x%x at %pS\n", opcode, insn); + BUG(); } static inline enum insn_type __sc_insn(bool null, bool tail) @@ -97,12 +103,12 @@ void arch_static_call_transform(void *site, void *tramp, void *func, bool tail) mutex_lock(&text_mutex); if (tramp) { - __static_call_validate(tramp, true); + __static_call_validate(tramp, true, true); __static_call_transform(tramp, __sc_insn(!func, true), func); } if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site) { - __static_call_validate(site, tail); + __static_call_validate(site, tail, false); __static_call_transform(site, __sc_insn(!func, tail), func); } |