Smack: check for SMACK xattr validity in smack_inode_setxattr

the following patch moves checks for SMACK xattr validity
from smack_inode_post_setxattr (which cannot return an error to the user)
to smack_inode_setxattr (which can return an error).

Signed-off-by: Etienne Basset <etienne.basset@numericable.fr>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 6 insertions, 5 deletions

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 921514902eca..98b3195347ab 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -609,8 +609,12 @@ static int smack_inode_setxattr(struct dentry *dentry, const char *name,
             strcmp(name, XATTR_NAME_SMACKIPOUT) == 0) {
                 if (!capable(CAP_MAC_ADMIN))
                         rc = -EPERM;
-                /* a label cannot be void and cannot begin with '-' */
-                if (size == 0 || (size > 0 && ((char *)value)[0] == '-'))
+                /*
+                 * check label validity here so import wont fail on
+                 * post_setxattr
+                 */
+                if (size == 0 || size >= SMK_LABELLEN ||
+                    smk_import(value, size) == NULL)
                         rc = -EINVAL;
         } else
                 rc = cap_inode_setxattr(dentry, name, value, size, flags);
@@ -644,9 +648,6 @@ static void smack_inode_post_setxattr(struct dentry *dentry, const char *name,
         if (strcmp(name, XATTR_NAME_SMACK))
                 return;
 
-        if (size >= SMK_LABELLEN)
-                return;
-
         isp = dentry->d_inode->i_security;
 
         /*