linux-kernel - [PATCH 2/2] ceph/inode: drop extra reference from ceph_get_reply_dir() in ceph_fill

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Message-Id: <20250901151448.726098-2-amarkuze@redhat.com>
Date: Mon,  1 Sep 2025 15:14:48 +0000
From: Alex Markuze <amarkuze@...hat.com>
To: ceph-devel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Slava.Dubeyko@....com,
	idryomov@...il.com,
	Alex Markuze <amarkuze@...hat.com>
Subject: [PATCH 2/2] ceph/inode: drop extra reference from ceph_get_reply_dir() in ceph_fill_trace()

ceph_get_reply_dir() may return a different, referenced inode when r_parent is stale and the parent directory lock is not held.
ceph_fill_trace() used that inode but failed to drop the reference when it differed from req->r_parent, leaking an inode reference.

Keep the directory inode in a local and iput() it at function end if it does not match req->r_parent.

Signed-off-by: Alex Markuze <amarkuze@...hat.com>
---
 fs/ceph/inode.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 470ee595ecf2..439c08ece283 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1585,6 +1585,7 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
 	struct ceph_fs_client *fsc = ceph_sb_to_fs_client(sb);
 	struct ceph_client *cl = fsc->client;
 	int err = 0;
+	struct inode *dir = NULL;
 
 	doutc(cl, "%p is_dentry %d is_target %d\n", req,
 	      rinfo->head->is_dentry, rinfo->head->is_target);
@@ -1601,7 +1602,11 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
 		 * r_parent may be stale, in cases when R_PARENT_LOCKED is not set,
 		 * so we need to get the correct inode
 		 */
-		struct inode *dir = ceph_get_reply_dir(sb, req->r_parent, rinfo);
+		dir = ceph_get_reply_dir(sb, req->r_parent, rinfo);
+		if (IS_ERR(dir)) {
+			err = PTR_ERR(dir);
+			goto done;
+		}
 		if (dir) {
 			err = ceph_fill_inode(dir, NULL, &rinfo->diri,
 					      rinfo->dirfrag, session, -1,
@@ -1869,6 +1874,9 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
 					    &dvino, ptvino);
 	}
 done:
+	/* Drop extra ref from ceph_get_reply_dir() if it returned a new inode */
+	if (!IS_ERR(dir) && dir && dir != req->r_parent)
+		iput(dir);
 	doutc(cl, "done err=%d\n", err);
 	return err;
 }
-- 
2.34.1