BACKPORT: Smack: fix behavior of smack_inode_listsecurity

Security operation ->inode_listsecurity is used for generating list of
available extended attributes for syscall listxattr. Currently it's used
only in nfs4 or if filesystem doesn't provide i_op->listxattr.

The list is the set of NULL-terminated names, one after the other.
This method must include zero byte at the and into result.

Also this function must return length even if string does not fit into
output buffer or it is NULL, see similar method in selinux and man listxattr.

Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@samsung.com>
(cherry-picked from upstream fd5c9d230d2ac8a2594dfd15f0cca678fd7a64c7)

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 438537c329154c3d63acc5f57b3396650bf2ffec..99bde57067f7a9522ea1d28925678444fb366910 100644 (file)
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1125,13 +1125,12 @@ static int smack_inode_getsecurity(const struct inode *inode,
 static int smack_inode_listsecurity(struct inode *inode, char *buffer,
                                    size_t buffer_size)
 {
-       int len = strlen(XATTR_NAME_SMACK);
+       int len = sizeof(XATTR_NAME_SMACK);
 
-       if (buffer != NULL && len <= buffer_size) {
+       if (buffer != NULL && len <= buffer_size)
                memcpy(buffer, XATTR_NAME_SMACK, len);
-               return len;
-       }
-       return -EINVAL;
+
+       return len;
 }
 
 /**