From: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com> mainline inclusion from mainline-5.8-rc2 commit 6f2cc1664db20676069cff27a461ccc97dbfd114 category: feature bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=27 CVE: NA --------------------------- In io_read() or io_write(), when io request is submitted successfully, it'll go through the below sequence: kfree(iovec); req->flags &= ~REQ_F_NEED_CLEANUP; return ret; But clearing REQ_F_NEED_CLEANUP might be unsafe. The io request may already have been completed, and then io_complete_rw_iopoll() and io_complete_rw() will be called, both of which will also modify req->flags if needed. This causes a race condition, with concurrent non-atomic modification of req->flags. To eliminate this race, in io_read() or io_write(), if io request is submitted successfully, we don't remove REQ_F_NEED_CLEANUP flag. If REQ_F_NEED_CLEANUP is set, we'll leave __io_req_aux_free() to the iovec cleanup work correspondingly. Cc: stable@vger.kernel.org Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: yangerkun <yangerkun@huawei.com> Reviewed-by: zhangyi (F) <yi.zhang@huawei.com> Signed-off-by: Cheng Jian <cj.chengjian@huawei.com> --- fs/io_uring.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 41db322af299..6856eec77aae 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -2669,8 +2669,8 @@ static int io_read(struct io_kiocb *req, bool force_nonblock) } } out_free: - kfree(iovec); - req->flags &= ~REQ_F_NEED_CLEANUP; + if (!(req->flags & REQ_F_NEED_CLEANUP)) + kfree(iovec); return ret; } @@ -2792,8 +2792,8 @@ static int io_write(struct io_kiocb *req, bool force_nonblock) } } out_free: - req->flags &= ~REQ_F_NEED_CLEANUP; - kfree(iovec); + if (!(req->flags & REQ_F_NEED_CLEANUP)) + kfree(iovec); return ret; } -- 2.25.1