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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>
This commit is contained in:
Jens Axboe 2023-10-21 12:30:29 -06:00
parent 8b51a3956d
commit 7644b1a1c9
1 changed files with 12 additions and 6 deletions
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18
io_uring/fdinfo.c
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@ -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);