6.4-stable review patch. If anyone has any objections, please let me know.
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From: Pavel Begunkov asml.silence@gmail.com
[ Upstream commit cfdbaa3a291d6fd2cb4a1a70d74e63b4abc2f5ec ]
cq_extra is protected by ->completion_lock, which io_get_sqe() misses. The bug is harmless as it doesn't happen in real life, requires invalid SQ index array and racing with submission, and only messes up the userspace, i.e. stall requests execution but will be cleaned up on ring destruction.
Fixes: 15641e427070f ("io_uring: don't cache number of dropped SQEs") Signed-off-by: Pavel Begunkov asml.silence@gmail.com Link: https://lore.kernel.org/r/66096d54651b1a60534bb2023f2947f09f50ef73.169153854... Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- io_uring/io_uring.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index a57bdf336ca8a..d029e578bdfe1 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2468,7 +2468,9 @@ static bool io_get_sqe(struct io_ring_ctx *ctx, const struct io_uring_sqe **sqe) }
/* drop invalid entries */ + spin_lock(&ctx->completion_lock); ctx->cq_extra--; + spin_unlock(&ctx->completion_lock); WRITE_ONCE(ctx->rings->sq_dropped, READ_ONCE(ctx->rings->sq_dropped) + 1); return false;