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kprobes: Set unoptimized flag after unoptimizing code

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Set the unoptimized flag after confirming the code is completely
unoptimized. Without this fix, when a kprobe hits the intermediate
modified instruction (the first byte is replaced by an INT3, but
later bytes can still be a jump address operand) while unoptimizing,
it can return to the middle byte of the modified code, which causes
an invalid instruction exception in the kernel.

Usually, this is a rare case, but if we put a probe on the function
call while text patching, it always causes a kernel panic as below:

 # echo p text_poke+5 > kprobe_events
 # echo 1 > events/kprobes/enable
 # echo 0 > events/kprobes/enable

invalid opcode: 0000 [#1] PREEMPT SMP PTI
 RIP: 0010:text_poke+0x9/0x50
 Call Trace:
  arch_unoptimize_kprobe+0x22/0x28
  arch_unoptimize_kprobes+0x39/0x87
  kprobe_optimizer+0x6e/0x290
  process_one_work+0x2a0/0x610
  worker_thread+0x28/0x3d0
  ? process_one_work+0x610/0x610
  kthread+0x10d/0x130
  ? kthread_park+0x80/0x80
  ret_from_fork+0x3a/0x50

text_poke() is used for patching the code in optprobes.

This can happen even if we blacklist text_poke() and other functions,
because there is a small time window during which we show the intermediate
code to other CPUs.

 [ mingo: Edited the changelog. ]

Tested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bristot@redhat.com
Fixes: 6274de4984 ("kprobes: Support delayed unoptimizing")
Link: https://lkml.kernel.org/r/157483422375.25881.13508326028469515760.stgit@devnote2
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Masami Hiramatsu 2019-11-27 14:57:04 +09:00 committed by Ingo Molnar
parent 285a54efe3
commit f66c0447cc
1 changed files with 3 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

4
kernel/kprobes.c
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@ -510,6 +510,8 @@ static void do_unoptimize_kprobes(void)
arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);
/* Loop free_list for disarming */
list_for_each_entry_safe(op, tmp, &freeing_list, list) {
/* Switching from detour code to origin */
op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
/* Disarm probes if marked disabled */
if (kprobe_disabled(&op->kp))
arch_disarm_kprobe(&op->kp);
@ -649,6 +651,7 @@ static void force_unoptimize_kprobe(struct optimized_kprobe *op)
{
lockdep_assert_cpus_held();
arch_unoptimize_kprobe(op);
op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
if (kprobe_disabled(&op->kp))
arch_disarm_kprobe(&op->kp);
}
@ -676,7 +679,6 @@ static void unoptimize_kprobe(struct kprobe *p, bool force)
return;
}
op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
if (!list_empty(&op->list)) {
/* Dequeue from the optimization queue */
list_del_init(&op->list);