lkml.org 
[lkml]   [2020]   [Mar]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.14 061/126] kprobes: Set unoptimized flag after unoptimizing code
Date
From: Masami Hiramatsu <mhiramat@kernel.org>

commit f66c0447cca1281116224d474cdb37d6a18e4b5b upstream.

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: 6274de4984a6 ("kprobes: Support delayed unoptimizing")
Link: https://lkml.kernel.org/r/157483422375.25881.13508326028469515760.stgit@devnote2
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/kprobes.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -523,6 +523,8 @@ 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);
@@ -662,6 +664,7 @@ static void force_unoptimize_kprobe(stru
{
lockdep_assert_cpus_held();
arch_unoptimize_kprobe(op);
+ op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
if (kprobe_disabled(&op->kp))
arch_disarm_kprobe(&op->kp);
}
@@ -689,7 +692,6 @@ static void unoptimize_kprobe(struct kpr
return;
}

- op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
if (!list_empty(&op->list)) {
/* Dequeue from the optimization queue */
list_del_init(&op->list);

\
 
 \ /
  Last update: 2020-03-10 14:08    [W:0.781 / U:0.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site