[PATCH 4.14 27/40] capabilities: fix potential memleak on error path from vfs_getxattr_alloc()

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

From: Gaosheng Cui <cuigaosheng1@huawei.com>

commit 8cf0a1bc12870d148ae830a4ba88cfdf0e879cee upstream.

In cap_inode_getsecurity(), we will use vfs_getxattr_alloc() to
complete the memory allocation of tmpbuf, if we have completed
the memory allocation of tmpbuf, but failed to call handler->get(...),
there will be a memleak in below logic:

  |-- ret = (int)vfs_getxattr_alloc(mnt_userns, ...)
    |           /* ^^^ alloc for tmpbuf */
    |-- value = krealloc(*xattr_value, error + 1, flags)
    |           /* ^^^ alloc memory */
    |-- error = handler->get(handler, ...)
    |           /* error! */
    |-- *xattr_value = value
    |           /* xattr_value is &tmpbuf (memory leak!) */

So we will try to free(tmpbuf) after vfs_getxattr_alloc() fails to fix it.

Cc: stable@vger.kernel.org
Fixes: 8db6c34f1dbc ("Introduce v3 namespaced file capabilities")
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
[PM: subject line and backtrace tweaks]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 security/commoncap.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -398,8 +398,10 @@ int cap_inode_getsecurity(struct inode *
 				 &tmpbuf, size, GFP_NOFS);
 	dput(dentry);
 
-	if (ret < 0 || !tmpbuf)
-		return ret;
+	if (ret < 0 || !tmpbuf) {
+		size = ret;
+		goto out_free;
+	}
 
 	fs_ns = inode->i_sb->s_user_ns;
 	cap = (struct vfs_cap_data *) tmpbuf;