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| author | Jens Axboe <axboe@kernel.dk> | 2019-10-25 10:04:25 -0600 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2019-10-25 10:58:45 -0600 |
| commit | 498ccd9eda49117c34e0041563d0da6ac40e52b8 (patch) | |
| tree | 1504976635c808ef89e58d5b9be1deffff68166c /fs/io_uring.c | |
| parent | 935d1e45908afb8853c497f2c2bbbb685dec51dc (diff) | |
| download | lwn-498ccd9eda49117c34e0041563d0da6ac40e52b8.tar.gz lwn-498ccd9eda49117c34e0041563d0da6ac40e52b8.zip | |
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: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'fs/io_uring.c')
| -rw-r--r-- | fs/io_uring.c | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c index 32f6598ecae9..292c4c733cbe 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -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; } |