We could race with SQ thread exit, and if we do, we'll hit a NULL pointer dereference. Park the SQPOLL thread while getting 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 Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> --- diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c index c53678875416..cd2a0c6b97c4 100644 --- a/io_uring/fdinfo.c +++ b/io_uring/fdinfo.c @@ -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 +143,18 @@ __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; + + io_sq_thread_park(sq); + if (sq->thread) { + sq_pid = task_pid_nr(sq->thread); + sq_cpu = task_cpu(sq->thread); + } + io_sq_thread_unpark(sq); } - 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); -- Jens Axboe
