io_uring/fdinfo: lock SQ thread while retrieving thread cpu/pid
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.
BUG=b/309761295
TEST=presubmit
RELEASE_NOTE=Fixed CVE-2023-46862 in the Linux kernel.
cos-patch: security-moderate
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218032
Change-Id: Ib4134c797e05723357dc20fb36f09a011541fd72
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: He Gao <hegao@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/61615
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Oleksandr Tymoshenko <ovt@google.com>
Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 325cf71..aad88dd 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -10426,7 +10426,7 @@
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;
@@ -10439,13 +10439,19 @@
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);
