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| author | Jens Axboe <axboe@kernel.dk> | 2023-10-21 12:30:29 -0600 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2023-10-25 07:44:14 -0600 |
| commit | 7644b1a1c9a7ae8ab99175989bfc8676055edb46 (patch) | |
| tree | dfa13e49521a00400a40c955f9f927a2e41c9af4 /io_uring | |
| parent | 8b51a3956d44ea6ade962874ade14de9a7d16556 (diff) | |
| download | lwn-7644b1a1c9a7ae8ab99175989bfc8676055edb46.tar.gz lwn-7644b1a1c9a7ae8ab99175989bfc8676055edb46.zip | |
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: Gabriel Krisman Bertazi <krisman@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'io_uring')
| -rw-r--r-- | io_uring/fdinfo.c | 18 |
1 files changed, 12 insertions, 6 deletions
diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c index c53678875416..f04a43044d91 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 +143,19 @@ __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); |