Commit e523a29c authored by Stefan Bühler's avatar Stefan Bühler Committed by Jens Axboe

io_uring: fix race condition reading SQ entries

A read memory barrier is required between reading SQ tail and reading
the actual data belonging to the SQ entry.

Userspace needs a matching write barrier between writing SQ entries and
updating SQ tail (using smp_store_release to update tail will do).
Signed-off-by: default avatarStefan Bühler <source@stbuehler.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 35fa71a0
...@@ -1739,7 +1739,8 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s) ...@@ -1739,7 +1739,8 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s)
head = ctx->cached_sq_head; head = ctx->cached_sq_head;
/* See comment at the top of this file */ /* See comment at the top of this file */
smp_rmb(); smp_rmb();
if (head == READ_ONCE(ring->r.tail)) /* make sure SQ entry isn't read before tail */
if (head == smp_load_acquire(&ring->r.tail))
return false; return false;
head = READ_ONCE(ring->array[head & ctx->sq_mask]); head = READ_ONCE(ring->array[head & ctx->sq_mask]);
......
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