From: Jens Axboe Date: Fri, 25 Oct 2019 16:04:25 +0000 (-0600) Subject: io_uring: used cached copies of sq->dropped and cq->overflow X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d366d732edf343f6010366c55cd26e37c4b91f0a;p=linux io_uring: used cached copies of sq->dropped and cq->overflow [ Upstream commit 498ccd9eda49117c34e0041563d0da6ac40e52b8 ] We currently use the ring values directly, but that can lead to issues if the application is malicious and changes these values on our behalf. Created in-kernel cached versions of them, and just overwrite the user side when we update them. This is similar to how we treat the sq/cq ring tail/head updates. Reported-by: Pavel Begunkov Reviewed-by: Pavel Begunkov Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- diff --git a/fs/io_uring.c b/fs/io_uring.c index 976ca7becfe8..ed223c33dd89 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -221,6 +221,7 @@ struct io_ring_ctx { unsigned sq_entries; unsigned sq_mask; unsigned sq_thread_idle; + unsigned cached_sq_dropped; struct io_uring_sqe *sq_sqes; struct list_head defer_list; @@ -237,6 +238,7 @@ struct io_ring_ctx { /* CQ ring */ struct io_cq_ring *cq_ring; unsigned cached_cq_tail; + atomic_t cached_cq_overflow; unsigned cq_entries; unsigned cq_mask; struct wait_queue_head cq_wait; @@ -431,7 +433,8 @@ static inline bool io_sequence_defer(struct io_ring_ctx *ctx, if ((req->flags & (REQ_F_IO_DRAIN|REQ_F_IO_DRAINED)) != REQ_F_IO_DRAIN) return false; - return req->sequence != ctx->cached_cq_tail + ctx->sq_ring->dropped; + return req->sequence != ctx->cached_cq_tail + ctx->sq_ring->dropped + + atomic_read(&ctx->cached_cq_overflow); } static struct io_kiocb *io_get_deferred_req(struct io_ring_ctx *ctx) @@ -511,9 +514,8 @@ static void io_cqring_fill_event(struct io_ring_ctx *ctx, u64 ki_user_data, WRITE_ONCE(cqe->res, res); WRITE_ONCE(cqe->flags, 0); } else { - unsigned overflow = READ_ONCE(ctx->cq_ring->overflow); - - WRITE_ONCE(ctx->cq_ring->overflow, overflow + 1); + WRITE_ONCE(ctx->cq_ring->overflow, + atomic_inc_return(&ctx->cached_cq_overflow)); } } @@ -2272,7 +2274,8 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s) /* drop invalid entries */ ctx->cached_sq_head++; - ring->dropped++; + ctx->cached_sq_dropped++; + WRITE_ONCE(ring->dropped, ctx->cached_sq_dropped); return false; }