Commit 4e51653d authored by Masami Hiramatsu (Google)'s avatar Masami Hiramatsu (Google) Committed by Ingo Molnar
Browse files

kprobes/x86: Use copy_from_kernel_nofault() to read from unsafe address 



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: cc66bb91 ("x86/ibt,kprobes: Cure sym+0 equals fentry woes")
Reported-by: default avatarQiang Zhang <zzqq0103.hey@gmail.com>
Tested-by: default avatarJinghao Jia <jinghao7@illinois.edu>
Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/171042945004.154897.2221804961882915806.stgit@devnote2
parent e3f269ed

arch/x86/kernel/kprobes/core.c

+10 −1
Original line number Diff line number Diff line
@@ -373,7 +373,16 @@ static bool 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;