linux-kernel - [PATCH v2] smb: client: Fix refcount leak for cifs_sb

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Message-ID: <aPBeBxTQLeyFl4mx@chcpu18>
Date: Thu, 16 Oct 2025 02:52:55 +0000
From: Shuhao Fu <sfual@....ust.hk>
To: Steve French <sfrench@...ba.org>, Steve French <smfrench@...il.com>
Cc: Markus Elfring <Markus.Elfring@....de>, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org, Bharath SM <bharathsm@...rosoft.com>,
        Paulo Alcantara <pc@...guebit.org>,
        Ronnie Sahlberg <ronniesahlberg@...il.com>,
        Shyam Prasad N <sprasad@...rosoft.com>, Tom Talpey <tom@...pey.com>,
        LKML <linux-kernel@...r.kernel.org>, kernel-janitors@...r.kernel.org
Subject: [PATCH v2] smb: client: Fix refcount leak for cifs_sb_tlink

Fix three refcount inconsistency issues related to `cifs_sb_tlink`. 

Comments for `cifs_sb_tlink` state that `cifs_put_tlink()` needs to be 
called after successful calls to `cifs_sb_tlink()`. Three calls fail to
update refcount accordingly, leading to possible resource leaks.

Fixes: 8ceb98437946 ("CIFS: Move rename to ops struct")
Fixes: 2f1afe25997f ("cifs: Use smb 2 - 3 and cifsacl mount options getacl functions")
Fixes: 366ed846df60 ("cifs: Use smb 2 - 3 and cifsacl mount options setacl function")
Signed-off-by: Shuhao Fu <sfual@....ust.hk>
---
Change in v2:
1. improved patch wording
2. nicer goto label naming

Link to v1: https://lore.kernel.org/linux-cifs/aOzRF9JB9VkBKapw@osx.local/
---
 fs/smb/client/inode.c   | 6 ++++--
 fs/smb/client/smb2ops.c | 8 ++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/smb/client/inode.c b/fs/smb/client/inode.c
index 239dd84a3..098a79b7a 100644
--- a/fs/smb/client/inode.c
+++ b/fs/smb/client/inode.c
@@ -2431,8 +2431,10 @@ cifs_do_rename(const unsigned int xid, struct dentry *from_dentry,
 	tcon = tlink_tcon(tlink);
 	server = tcon->ses->server;
 
-	if (!server->ops->rename)
-		return -ENOSYS;
+	if (!server->ops->rename) {
+		rc = -ENOSYS;
+		goto do_rename_exit;
+	}
 
 	/* try path-based rename first */
 	rc = server->ops->rename(xid, tcon, from_dentry,
diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 7c392cf59..00b3f769e 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -3212,8 +3212,7 @@ get_smb2_acl_by_path(struct cifs_sb_info *cifs_sb,
 	utf16_path = cifs_convert_path_to_utf16(path, cifs_sb);
 	if (!utf16_path) {
 		rc = -ENOMEM;
-		free_xid(xid);
-		return ERR_PTR(rc);
+		goto put_tlink;
 	}
 
 	oparms = (struct cifs_open_parms) {
@@ -3245,6 +3244,7 @@ get_smb2_acl_by_path(struct cifs_sb_info *cifs_sb,
 		SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);
 	}
 
+put_tlink:
 	cifs_put_tlink(tlink);
 	free_xid(xid);
 
@@ -3285,8 +3285,7 @@ set_smb2_acl(struct smb_ntsd *pnntsd, __u32 acllen,
 	utf16_path = cifs_convert_path_to_utf16(path, cifs_sb);
 	if (!utf16_path) {
 		rc = -ENOMEM;
-		free_xid(xid);
-		return rc;
+		goto put_tlink;
 	}
 
 	oparms = (struct cifs_open_parms) {
@@ -3307,6 +3306,7 @@ set_smb2_acl(struct smb_ntsd *pnntsd, __u32 acllen,
 		SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);
 	}
 
+put_tlink:
 	cifs_put_tlink(tlink);
 	free_xid(xid);
 	return rc;
-- 
2.39.5 (Apple Git-154)