From: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
commit 54aa7f2330b82884f4a1afce0220add6e8312f8b upstream.
Heming reported a BUG when using io_uring doing link-cp on ocfs2. [1]
Do the following steps can reproduce this BUG:
mount -t ocfs2 /dev/vdc /mnt/ocfs2
cp testfile /mnt/ocfs2/
./link-cp /mnt/ocfs2/testfile /mnt/ocfs2/testfile.1
umount /mnt/ocfs2
Then umount will fail, and it outputs:
umount: /mnt/ocfs2: target is busy.
While tracing umount, it blames mnt_get_count() not return as expected.
Do a deep investigation for fget()/fput() on related code flow, I've
finally found that fget() leaks since ocfs2 doesn't support nowait
buffered read.
io_issue_sqe
|-io_assign_file // do fget() first
|-io_read
|-io_iter_do_read
|-ocfs2_file_read_iter // return -EOPNOTSUPP
|-kiocb_done
|-io_rw_done
|-__io_complete_rw_common // set REQ_F_REISSUE
|-io_resubmit_prep
|-io_req_prep_async // override req->file, leak happens
This was introduced by commit a196c78b5443 in v5.18. Fix it by don't
re-assign req->file if it has already been assigned.
[1] https://lore.kernel.org/ocfs2-devel/ab580a75-91c8-d68a-3455-40361be1bfa8@xxxxxxxxxxxxxxxxx/T/#t
Fixes: a196c78b5443 ("io_uring: assign non-fixed early for async work")
Cc: <stable@xxxxxxxxxxxxxxx>
Reported-by: Heming Zhao <heming.zhao@xxxxxxxx>
Signed-off-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
Cc: Xiaoguang Wang <xiaoguang.wang@xxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230228045459.13524-1-joseph.qi@xxxxxxxxxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
io_uring/io_uring.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1728,7 +1728,7 @@ int io_req_prep_async(struct io_kiocb *r
const struct io_op_def *def = &io_op_defs[req->opcode];
/* assign early for deferred execution for non-fixed file */
- if (def->needs_file && !(req->flags & REQ_F_FIXED_FILE))
+ if (def->needs_file && !(req->flags & REQ_F_FIXED_FILE) && !req->file)
req->file = io_file_get_normal(req, req->cqe.fd);
if (!def->prep_async)
return 0;
