[PATCH 4.14 47/54] uprobes/x86: Remove incorrect WARN_ON() in uprobe_init_insn()

From: Greg Kroah-Hartman
Date: Mon Jul 16 2018 - 03:51:26 EST


4.14-stable review patch. If anyone has any objections, please let me know.

------------------

From: Oleg Nesterov <oleg@xxxxxxxxxx>

commit 90718e32e1dcc2479acfa208ccfc6442850b594c upstream.

insn_get_length() has the side-effect of processing the entire instruction
but only if it was decoded successfully, otherwise insn_complete() can fail
and in this case we need to just return an error without warning.

Reported-by: syzbot+30d675e3ca03c1c351e7@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Reviewed-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: syzkaller-bugs@xxxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/lkml/20180518162739.GA5559@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
arch/x86/kernel/uprobes.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -290,7 +290,7 @@ static int uprobe_init_insn(struct arch_
insn_init(insn, auprobe->insn, sizeof(auprobe->insn), x86_64);
/* has the side-effect of processing the entire instruction */
insn_get_length(insn);
- if (WARN_ON_ONCE(!insn_complete(insn)))
+ if (!insn_complete(insn))
return -ENOEXEC;

if (is_prefix_bad(insn))