capabilities: fix potential memleak on error path from vfs_getxattr_alloc()

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>

diff --git a/security/commoncap.c b/security/commoncap.c
index 5fc8986..bc751fa 100644 (file)
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -401,8 +401,10 @@ int cap_inode_getsecurity(struct user_namespace *mnt_userns,
                                      &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;