This is a note to let you know that I've just added the patch titled
io_uring/fdinfo: lock SQ thread while retrieving thread cpu/pid
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
io_uring-fdinfo-lock-sq-thread-while-retrieving-thread-cpu-pid.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7644b1a1c9a7ae8ab99175989bfc8676055edb46 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@xxxxxxxxx>
Date: Sat, 21 Oct 2023 12:30:29 -0600
Subject: io_uring/fdinfo: lock SQ thread while retrieving thread cpu/pid
From: Jens Axboe <axboe@xxxxxxxxx>
commit 7644b1a1c9a7ae8ab99175989bfc8676055edb46 upstream.
We could race with SQ thread exit, and if we do, we'll hit a NULL pointer
dereference when the thread is cleared. Grab the SQPOLL data lock before
attempting to get the task cpu and pid for fdinfo, this ensures we have a
stable view of it.
Cc: stable@xxxxxxxxxxxxxxx
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218032
Reviewed-by: Gabriel Krisman Bertazi <krisman@xxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: He Gao <hegao@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
io_uring/io_uring.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -10411,7 +10411,7 @@ static int io_uring_show_cred(struct seq
static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
{
- struct io_sq_data *sq = NULL;
+ int sq_pid = -1, sq_cpu = -1;
bool has_lock;
int i;
@@ -10424,13 +10424,19 @@ static void __io_uring_show_fdinfo(struc
has_lock = mutex_trylock(&ctx->uring_lock);
if (has_lock && (ctx->flags & IORING_SETUP_SQPOLL)) {
- sq = ctx->sq_data;
- if (!sq->thread)
- sq = NULL;
+ struct io_sq_data *sq = ctx->sq_data;
+
+ if (mutex_trylock(&sq->lock)) {
+ if (sq->thread) {
+ sq_pid = task_pid_nr(sq->thread);
+ sq_cpu = task_cpu(sq->thread);
+ }
+ mutex_unlock(&sq->lock);
+ }
}
- seq_printf(m, "SqThread:\t%d\n", sq ? task_pid_nr(sq->thread) : -1);
- seq_printf(m, "SqThreadCpu:\t%d\n", sq ? task_cpu(sq->thread) : -1);
+ seq_printf(m, "SqThread:\t%d\n", sq_pid);
+ seq_printf(m, "SqThreadCpu:\t%d\n", sq_cpu);
seq_printf(m, "UserFiles:\t%u\n", ctx->nr_user_files);
for (i = 0; has_lock && i < ctx->nr_user_files; i++) {
struct file *f = io_file_from_index(ctx, i);
Patches currently in stable-queue which might be from axboe@xxxxxxxxx are
queue-5.15/io_uring-fdinfo-lock-sq-thread-while-retrieving-thread-cpu-pid.patch
