Message-Id: <20250904101234.1258643-1-amarkuze@redhat.com>
Date: Thu,  4 Sep 2025 10:12:34 +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 v2 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 | 30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 470ee595ecf2..cffa2cd7b530 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1584,6 +1584,7 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
 	struct ceph_vino tvino, dvino;
 	struct ceph_fs_client *fsc = ceph_sb_to_fs_client(sb);
 	struct ceph_client *cl = fsc->client;
+	struct inode *parent_dir = NULL;
 	int err = 0;
 
 	doutc(cl, "%p is_dentry %d is_target %d\n", req,
@@ -1601,9 +1602,13 @@ 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);
-		if (dir) {
-			err = ceph_fill_inode(dir, NULL, &rinfo->diri,
+		parent_dir = ceph_get_reply_dir(sb, req->r_parent, rinfo);
+		if (unlikely(IS_ERR(parent_dir))) {
+			err = PTR_ERR(parent_dir);
+			goto done;
+		}
+		if (parent_dir) {
+			err = ceph_fill_inode(parent_dir, NULL, &rinfo->diri,
 					      rinfo->dirfrag, session, -1,
 					      &req->r_caps_reservation);
 			if (err < 0)
@@ -1612,14 +1617,14 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
 			WARN_ON_ONCE(1);
 		}
 
-		if (dir && req->r_op == CEPH_MDS_OP_LOOKUPNAME &&
+		if (parent_dir && req->r_op == CEPH_MDS_OP_LOOKUPNAME &&
 		    test_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags) &&
 		    !test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags)) {
 			bool is_nokey = false;
 			struct qstr dname;
 			struct dentry *dn, *parent;
 			struct fscrypt_str oname = FSTR_INIT(NULL, 0);
-			struct ceph_fname fname = { .dir	= dir,
+			struct ceph_fname fname = { .dir	= parent_dir,
 						    .name	= rinfo->dname,
 						    .ctext	= rinfo->altname,
 						    .name_len	= rinfo->dname_len,
@@ -1628,10 +1633,10 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
 			BUG_ON(!rinfo->head->is_target);
 			BUG_ON(req->r_dentry);
 
-			parent = d_find_any_alias(dir);
+			parent = d_find_any_alias(parent_dir);
 			BUG_ON(!parent);
 
-			err = ceph_fname_alloc_buffer(dir, &oname);
+			err = ceph_fname_alloc_buffer(parent_dir, &oname);
 			if (err < 0) {
 				dput(parent);
 				goto done;
@@ -1640,7 +1645,7 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
 			err = ceph_fname_to_usr(&fname, NULL, &oname, &is_nokey);
 			if (err < 0) {
 				dput(parent);
-				ceph_fname_free_buffer(dir, &oname);
+				ceph_fname_free_buffer(parent_dir, &oname);
 				goto done;
 			}
 			dname.name = oname.name;
@@ -1659,7 +1664,7 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
 				      dname.len, dname.name, dn);
 				if (!dn) {
 					dput(parent);
-					ceph_fname_free_buffer(dir, &oname);
+					ceph_fname_free_buffer(parent_dir, &oname);
 					err = -ENOMEM;
 					goto done;
 				}
@@ -1674,12 +1679,12 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req)
 				    ceph_snap(d_inode(dn)) != tvino.snap)) {
 				doutc(cl, " dn %p points to wrong inode %p\n",
 				      dn, d_inode(dn));
-				ceph_dir_clear_ordered(dir);
+				ceph_dir_clear_ordered(parent_dir);
 				d_delete(dn);
 				dput(dn);
 				goto retry_lookup;
 			}
-			ceph_fname_free_buffer(dir, &oname);
+			ceph_fname_free_buffer(parent_dir, &oname);
 
 			req->r_dentry = dn;
 			dput(parent);
@@ -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 (unlikely(!IS_ERR_OR_NULL(parent_dir) && parent_dir != req->r_parent))
+		iput(parent_dir);
 	doutc(cl, "done err=%d\n", err);
 	return err;
 }
-- 
2.34.1

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