From: Masami Hiramatsu (Google) <mhira...@kernel.org> 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.
Reported-by: Qiang Zhang <zzqq0103....@gmail.com> Closes: https://lore.kernel.org/all/cakhosas2rof6vqvbw_lg_j3qnku0canzr2qmy4et7r5lo8m...@mail.gmail.com/ Fixes: cc66bb914578 ("x86/ibt,kprobes: Cure sym+0 equals fentry woes") Signed-off-by: Masami Hiramatsu (Google) <mhira...@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 a0ce46c0a2d8..a885eea3bd34 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 safely accessed yet, use + * copy_from_kernel_nofault() to get the instruction. + */ + if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(u32))) + return 0; + + if (is_endbr(insn)) { *on_func_entry = !offset || offset == 4; if (*on_func_entry) offset = 4;
