linux-kernel - [PATCH] ksmbd: fix reference count leak in smb_check_perm

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Message-Id: <20220429081121.1640-1-xiongx18@fudan.edu.cn>
Date:   Fri, 29 Apr 2022 16:11:22 +0800
From:   Xin Xiong <xiongx18@...an.edu.cn>
To:     Namjae Jeon <linkinjeon@...nel.org>,
        Steve French <sfrench@...ba.org>,
        Hyunchul Lee <hyc.lee@...il.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        linux-cifs@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     yuanxzhang@...an.edu.cn, Xin Xiong <xiongx18@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>
Subject: [PATCH] ksmbd: fix reference count leak in smb_check_perm_dacl()

The issue happens in a specific path in smb_check_perm_dacl(). When
"id" and "uid" have the same value, the function simply jumps out of
the loop without decrementing the reference count of the object
"posix_acls", which is increased by get_acl() earlier. This may
result in memory leaks.

Fix it by decreasing the reference count of "posix_acls" before
jumping to label "check_access_bits".

Fixes: 777cad1604d6 ("ksmbd: remove select FS_POSIX_ACL in Kconfig")
Signed-off-by: Xin Xiong <xiongx18@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
---
 fs/ksmbd/smbacl.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/ksmbd/smbacl.c b/fs/ksmbd/smbacl.c
index 6ecf55ea1fed..38f23bf981ac 100644
--- a/fs/ksmbd/smbacl.c
+++ b/fs/ksmbd/smbacl.c
@@ -1261,6 +1261,7 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, struct path *path,
 					if (!access_bits)
 						access_bits =
 							SET_MINIMUM_RIGHTS;
+					posix_acl_release(posix_acls);
 					goto check_access_bits;
 				}
 			}
-- 
2.25.1