Commit 7644b1a1 authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring/fdinfo: lock SQ thread while retrieving thread cpu/pid 

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@vger.kernel.org
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218032


Reviewed-by: default avatarGabriel Krisman Bertazi <krisman@suse.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 8b51a395

io_uring/fdinfo.c

+12 −6
Original line number Diff line number Diff line
@@ -53,7 +53,6 @@ static __cold int io_uring_show_cred(struct seq_file *m, unsigned int id, 
__cold void io_uring_show_fdinfo(struct seq_file *m, struct file *f)

{

	struct io_ring_ctx *ctx = f->private_data;

	struct io_sq_data *sq = NULL;

	struct io_overflow_cqe *ocqe;

	struct io_rings *r = ctx->rings;

	unsigned int sq_mask = ctx->sq_entries - 1, cq_mask = ctx->cq_entries - 1;
@@ -64,6 +63,7 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *f) 
	unsigned int cq_shift = 0;

	unsigned int sq_shift = 0;

	unsigned int sq_entries, cq_entries;

	int sq_pid = -1, sq_cpu = -1;

	bool has_lock;

	unsigned int i;
@@ -143,13 +143,19 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *f) 
	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->file_table, i);