From 75013fb16f8484898eaa8d0b08fed942d790f029 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Wed, 1 Mar 2017 01:23:24 +0900 Subject: [PATCH] kprobes/x86: Fix kernel panic when certain exception-handling addresses are probed Fix to the exception table entry check by using probed address instead of the address of copied instruction. This bug may cause unexpected kernel panic if user probe an address where an exception can happen which should be fixup by __ex_table (e.g. copy_from_user.) Unless user puts a kprobe on such address, this doesn't cause any problem. This bug has been introduced years ago, by commit: 464846888d9a ("x86/kprobes: Fix a bug which can modify kernel code permanently"). Signed-off-by: Masami Hiramatsu Cc: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: 464846888d9a ("x86/kprobes: Fix a bug which can modify kernel code permanently") Link: http://lkml.kernel.org/r/148829899399.28855.12581062400757221722.stgit@devbox Signed-off-by: Ingo Molnar --- arch/x86/kernel/kprobes/common.h | 2 +- arch/x86/kernel/kprobes/core.c | 6 +++--- arch/x86/kernel/kprobes/opt.c | 2 +- 3 files changed, 5 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/kprobes/common.h b/arch/x86/kernel/kprobes/common.h index c6ee63f927ab..d688826e5736 100644 --- a/arch/x86/kernel/kprobes/common.h +++ b/arch/x86/kernel/kprobes/common.h @@ -67,7 +67,7 @@ #endif /* Ensure if the instruction can be boostable */ -extern int can_boost(kprobe_opcode_t *instruction); +extern int can_boost(kprobe_opcode_t *instruction, void *addr); /* Recover instruction if given address is probed */ extern unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr); diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 520b8dfe1640..88b3c942473d 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -166,12 +166,12 @@ NOKPROBE_SYMBOL(skip_prefixes); * Returns non-zero if opcode is boostable. * RIP relative instructions are adjusted at copying time in 64 bits mode */ -int can_boost(kprobe_opcode_t *opcodes) +int can_boost(kprobe_opcode_t *opcodes, void *addr) { kprobe_opcode_t opcode; kprobe_opcode_t *orig_opcodes = opcodes; - if (search_exception_tables((unsigned long)opcodes)) + if (search_exception_tables((unsigned long)addr)) return 0; /* Page fault may occur on this address. */ retry: @@ -416,7 +416,7 @@ static int arch_copy_kprobe(struct kprobe *p) * __copy_instruction can modify the displacement of the instruction, * but it doesn't affect boostable check. */ - if (can_boost(p->ainsn.insn)) + if (can_boost(p->ainsn.insn, p->addr)) p->ainsn.boostable = 0; else p->ainsn.boostable = -1; diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c index 3d1bee9d6a72..3e7c6e5a08ff 100644 --- a/arch/x86/kernel/kprobes/opt.c +++ b/arch/x86/kernel/kprobes/opt.c @@ -178,7 +178,7 @@ static int copy_optimized_instructions(u8 *dest, u8 *src) while (len < RELATIVEJUMP_SIZE) { ret = __copy_instruction(dest + len, src + len); - if (!ret || !can_boost(dest + len)) + if (!ret || !can_boost(dest + len, src + len)) return -EINVAL; len += ret; }