[PATCH 6.18 0645/1250] netfs: Fix subreq ref leak

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Howells <dhowells@redhat.com>

[ Upstream commit 3c30087e27598d9d359763e8be9bd3017fe08348 ]

Fix a subrequest ref leak in netfs_unbuffered_write() in the event that
subreq->io_iter ends up zero length during preparation.

Fixes: a0b4c7a49137e ("netfs: Fix unbuffered/DIO writes to dispatch subrequests in strict sequence")
Link: https://sashiko.dev/#/patchset/20260824120224.504575-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://patch.msgid.link/20260827134304.2075713-6-dhowells@redhat.com
Acked-by: Paulo Alcantara <pc@manguebit.org>
cc: Paulo Alcantara <pc@manguebit.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/netfs/direct_write.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/netfs/direct_write.c b/fs/netfs/direct_write.c
index 6cba5bd60361d..abc8f6955fd50 100644
--- a/fs/netfs/direct_write.c
+++ b/fs/netfs/direct_write.c
@@ -121,8 +121,14 @@ static int netfs_unbuffered_write(struct netfs_io_request *wreq)
 		}
 
 		iov_iter_truncate(&subreq->io_iter, wreq->len - wreq->transferred);
-		if (!iov_iter_count(&subreq->io_iter))
+		if (!iov_iter_count(&subreq->io_iter)) {
+			pr_warn("netfs: Unexpected zero-length iterator R=%08x\n",
+				wreq->debug_id);
+			__set_bit(NETFS_SREQ_FAILED, &subreq->flags);
+			netfs_write_subrequest_terminated(subreq, -EIO);
+			wreq->error = -EIO;
 			break;
+		}
 
 		subreq->len = netfs_limit_iter(&subreq->io_iter, 0,
 					       stream->sreq_max_len,
-- 
2.53.0