Commit 498ccd9e authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring: used cached copies of sq->dropped and cq->overflow 



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: default avatarPavel Begunkov <asml.silence@gmail.com>
Reviewed-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 935d1e45

fs/io_uring.c

+8 −5
Original line number Diff line number Diff line
@@ -197,6 +197,7 @@ 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;
@@ -212,6 +213,7 @@ struct io_ring_ctx { 


	struct {

		unsigned		cached_cq_tail;

		atomic_t		cached_cq_overflow;

		unsigned		cq_entries;

		unsigned		cq_mask;

		struct wait_queue_head	cq_wait;
@@ -420,7 +422,8 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p) 
static inline bool __io_sequence_defer(struct io_ring_ctx *ctx,

				       struct io_kiocb *req)

{

	return req->sequence != ctx->cached_cq_tail + ctx->rings->sq_dropped;

	return req->sequence != ctx->cached_cq_tail + ctx->cached_sq_dropped

					+ atomic_read(&ctx->cached_cq_overflow);

}



static inline bool io_sequence_defer(struct io_ring_ctx *ctx,
@@ -567,9 +570,8 @@ 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->rings->cq_overflow);



		WRITE_ONCE(ctx->rings->cq_overflow, overflow + 1);

		WRITE_ONCE(ctx->rings->cq_overflow,

				atomic_inc_return(&ctx->cached_cq_overflow));

	}

}
@@ -2564,7 +2566,8 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s) 


	/* drop invalid entries */

	ctx->cached_sq_head++;

	rings->sq_dropped++;

	ctx->cached_sq_dropped++;

	WRITE_ONCE(rings->sq_dropped, ctx->cached_sq_dropped);

	return false;

}

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