From: "Masami Hiramatsu (Google)" <[email protected]>
commit 4fbd2f83fda0ca44a2ec6421ca3508b355b31858 upstream.
Since forcibly unoptimized kprobes will be put on the freeing_list directly
in the unoptimize_kprobe(), do_unoptimize_kprobes() must continue to check
the freeing_list even if unoptimizing_list is empty.
This bug can happen if a kprobe is put in an instruction which is in the
middle of the jump-replaced instruction sequence of an optprobe, *and* the
optprobe is recently unregistered and queued on unoptimizing_list.
In this case, the optprobe will be unoptimized forcibly (means immediately)
and put it into the freeing_list, expecting the optprobe will be handled in
do_unoptimize_kprobe().
But if there is no other optprobes on the unoptimizing_list, current code
returns from the do_unoptimize_kprobe() soon and does not handle the
optprobe which is on the freeing_list. Then the optprobe will hit the
WARN_ON_ONCE() in the do_free_cleaned_kprobes(), because it is not handled
in the latter loop of the do_unoptimize_kprobe().
To solve this issue, do not return from do_unoptimize_kprobes() immediately
even if unoptimizing_list is empty.
Moreover, this change affects another case. kill_optimized_kprobes() expects
kprobe_optimizer() will just free the optprobe on freeing_list.
So I changed it to just do list_move() to freeing_list if optprobes are on
unoptimizing list. And the do_unoptimize_kprobe() will skip
arch_disarm_kprobe() if the probe on freeing_list has gone flag.
Link: https://lore.kernel.org/all/[email protected]/
Link: https://lore.kernel.org/all/167448024501.3253718.13037333683110512967.stgit@devnote3/
Fixes: e4add247789e ("kprobes: Fix optimize_kprobe()/unoptimize_kprobe() cancellation logic")
Reported-by: Pengfei Xu <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Cc: [email protected]
Acked-by: Steven Rostedt (Google) <[email protected]>
[fp: adjust comment conflict regarding commit 223a76b268c9 ("kprobes: Fix
coding style issues")]
Signed-off-by: Fedor Pchelkin <[email protected]>
---
kernel/kprobes.c | 23 ++++++++++-------------
1 file changed, 10 insertions(+), 13 deletions(-)
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 07d36cee2a80..5d713a7d7e87 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -549,17 +549,15 @@ static void do_unoptimize_kprobes(void)
/* See comment in do_optimize_kprobes() */
lockdep_assert_cpus_held();
- /* Unoptimization must be done anytime */
- if (list_empty(&unoptimizing_list))
- return;
+ if (!list_empty(&unoptimizing_list))
+ arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);
- arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);
- /* Loop free_list for disarming */
+ /* Loop on 'freeing_list' for disarming and removing from kprobe hash list */
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))
+ /* Disarm probes if marked disabled and not gone */
+ if (kprobe_disabled(&op->kp) && !kprobe_gone(&op->kp))
arch_disarm_kprobe(&op->kp);
if (kprobe_unused(&op->kp)) {
/*
@@ -788,14 +786,13 @@ static void kill_optimized_kprobe(struct kprobe *p)
op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
if (kprobe_unused(p)) {
- /* Enqueue if it is unused */
- list_add(&op->list, &freeing_list);
/*
- * Remove unused probes from the hash list. After waiting
- * for synchronization, this probe is reclaimed.
- * (reclaiming is done by do_free_cleaned_kprobes().)
+ * Unused kprobe is on unoptimizing or freeing list. We move it
+ * to freeing_list and let the kprobe_optimizer() remove it from
+ * the kprobe hash list and free it.
*/
- hlist_del_rcu(&op->kp.hlist);
+ if (optprobe_queued_unopt(op))
+ list_move(&op->list, &freeing_list);
}
/* Don't touch the code, because it is already freed. */
--
2.39.2
On Mon, Jan 22, 2024 at 02:30:31PM +0300, Fedor Pchelkin wrote:
> From: "Masami Hiramatsu (Google)" <[email protected]>
>
> commit 4fbd2f83fda0ca44a2ec6421ca3508b355b31858 upstream.
>
> Since forcibly unoptimized kprobes will be put on the freeing_list directly
> in the unoptimize_kprobe(), do_unoptimize_kprobes() must continue to check
> the freeing_list even if unoptimizing_list is empty.
>
> This bug can happen if a kprobe is put in an instruction which is in the
> middle of the jump-replaced instruction sequence of an optprobe, *and* the
> optprobe is recently unregistered and queued on unoptimizing_list.
> In this case, the optprobe will be unoptimized forcibly (means immediately)
> and put it into the freeing_list, expecting the optprobe will be handled in
> do_unoptimize_kprobe().
> But if there is no other optprobes on the unoptimizing_list, current code
> returns from the do_unoptimize_kprobe() soon and does not handle the
> optprobe which is on the freeing_list. Then the optprobe will hit the
> WARN_ON_ONCE() in the do_free_cleaned_kprobes(), because it is not handled
> in the latter loop of the do_unoptimize_kprobe().
>
> To solve this issue, do not return from do_unoptimize_kprobes() immediately
> even if unoptimizing_list is empty.
>
> Moreover, this change affects another case. kill_optimized_kprobes() expects
> kprobe_optimizer() will just free the optprobe on freeing_list.
> So I changed it to just do list_move() to freeing_list if optprobes are on
> unoptimizing list. And the do_unoptimize_kprobe() will skip
> arch_disarm_kprobe() if the probe on freeing_list has gone flag.
>
> Link: https://lore.kernel.org/all/[email protected]/
> Link: https://lore.kernel.org/all/167448024501.3253718.13037333683110512967.stgit@devnote3/
>
> Fixes: e4add247789e ("kprobes: Fix optimize_kprobe()/unoptimize_kprobe() cancellation logic")
> Reported-by: Pengfei Xu <[email protected]>
> Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
> Cc: [email protected]
> Acked-by: Steven Rostedt (Google) <[email protected]>
> [fp: adjust comment conflict regarding commit 223a76b268c9 ("kprobes: Fix
> coding style issues")]
> Signed-off-by: Fedor Pchelkin <[email protected]>
> ---
> kernel/kprobes.c | 23 ++++++++++-------------
> 1 file changed, 10 insertions(+), 13 deletions(-)
Now queued up, thanks.
greg k-h