We already check if the chosen starting offset for the buffer IDs fit within an unsigned short, as 65535 is the maximum value for a provided buffer. But if the caller asks to add N buffers at offset M, and M + N would exceed the size of the unsigned short, we simply add buffers with wrapping around the ID. This is not necessarily a bug and could in fact be a valid use case, but it seems confusing and inconsistent with the initial check for starting offset. Let's check for wrap consistently, and error the addition if we do need to wrap. Reported-by: Oliver Lang <Oliver.Lang@xxxxxxxxxxxxxxxxxxx> Link: https://github.com/axboe/liburing/issues/726 Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> --- diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c index 25cd724ade18..e2c46889d5fa 100644 --- a/io_uring/kbuf.c +++ b/io_uring/kbuf.c @@ -346,6 +346,8 @@ int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe tmp = READ_ONCE(sqe->off); if (tmp > USHRT_MAX) return -E2BIG; + if (tmp + p->nbufs >= USHRT_MAX) + return -EINVAL; p->bid = tmp; return 0; } -- Jens Axboe
