6.5-stable review patch. If anyone has any objections, please let me know. ------------------ 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: Sasha Levin <sashal@xxxxxxxxxx> --- io_uring/fdinfo.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c index 76c279b13aee4..b603a06f7103d 100644 --- a/io_uring/fdinfo.c +++ b/io_uring/fdinfo.c @@ -49,7 +49,6 @@ static __cold int io_uring_show_cred(struct seq_file *m, unsigned int id, static __cold void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m) { - 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; @@ -60,6 +59,7 @@ static __cold void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, 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; @@ -137,13 +137,19 @@ static __cold void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, 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); -- 2.42.0
