From 9eab5008db6c98273acaa0e0dde0fdb25848217e Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 28 Aug 2023 18:47:31 -0400 Subject: [PATCH] io_uring: kiocb_done() should *not* trust ->ki_pos if ->{read,write}_iter() failed [ Upstream commit 1939316bf988f3e49a07d9c4dd6f660bf4daa53d ] ->ki_pos value is unreliable in such cases. For an obvious example, consider O_DSYNC write - we feed the data to page cache and start IO, then we make sure it's completed. Update of ->ki_pos is dealt with by the first part; failure in the second ends up with negative value returned _and_ ->ki_pos left advanced as if sync had been successful. In the same situation write(2) does not advance the file position at all. Reviewed-by: Christian Brauner Reviewed-by: Jens Axboe Signed-off-by: Al Viro Signed-off-by: Sasha Levin --- io_uring/rw.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/io_uring/rw.c b/io_uring/rw.c index 0218fae..0133db6 100644 --- a/io_uring/rw.c +++ b/io_uring/rw.c @@ -326,7 +326,7 @@ static int kiocb_done(struct io_kiocb *req, ssize_t ret, struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw); unsigned final_ret = io_fixup_rw_res(req, ret); - if (req->flags & REQ_F_CUR_POS) + if (ret >= 0 && req->flags & REQ_F_CUR_POS) req->file->f_pos = rw->kiocb.ki_pos; if (ret >= 0 && (rw->kiocb.ki_complete == io_complete_rw)) { if (!__io_complete_rw_common(req, ret)) { -- 2.7.4