6.8-stable review patch. If anyone has any objections, please let me know.
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From: Masami Hiramatsu (Google) mhiramat@kernel.org
[ Upstream commit 4e51653d5d871f40f1bd5cf95cc7f2d8b33d063b ]
Read from an unsafe address with copy_from_kernel_nofault() in arch_adjust_kprobe_addr() because this function is used before checking the address is in text or not. Syzcaller bot found a bug and reported the case if user specifies inaccessible data area, arch_adjust_kprobe_addr() will cause a kernel panic.
[ mingo: Clarified the comment. ]
Fixes: cc66bb914578 ("x86/ibt,kprobes: Cure sym+0 equals fentry woes") Reported-by: Qiang Zhang zzqq0103.hey@gmail.com Tested-by: Jinghao Jia jinghao7@illinois.edu Signed-off-by: Masami Hiramatsu (Google) mhiramat@kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Link: https://lore.kernel.org/r/171042945004.154897.2221804961882915806.stgit@devn... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/kprobes/core.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index a0ce46c0a2d88..a6a3475e1d609 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -335,7 +335,16 @@ static int can_probe(unsigned long paddr) kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offset, bool *on_func_entry) { - if (is_endbr(*(u32 *)addr)) { + u32 insn; + + /* + * Since 'addr' is not guaranteed to be safe to access, use + * copy_from_kernel_nofault() to read the instruction: + */ + if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(u32))) + return NULL; + + if (is_endbr(insn)) { *on_func_entry = !offset || offset == 4; if (*on_func_entry) offset = 4;