Smack: fuse mount hang fix

The d_instantiate hook for Smack can hang on the root inode of a
filesystem if the file system code has not really done all the set-up.
Fuse is known to encounter this problem.

This change detects an attempt to instantiate a root inode and addresses
it early in the processing, before any attempt is made to do something
that might hang.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Tested-by: Luiz Fernando N. Capitulino <lcapitulino@mandriva.com.br>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index b5c8f9237008..4a09293efa00 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1881,6 +1881,18 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
         final = sbsp->smk_default;
 
         /*
+         * If this is the root inode the superblock
+         * may be in the process of initialization.
+         * If that is the case use the root value out
+         * of the superblock.
+         */
+        if (opt_dentry->d_parent == opt_dentry) {
+                isp->smk_inode = sbsp->smk_root;
+                isp->smk_flags |= SMK_INODE_INSTANT;
+                goto unlockandout;
+        }
+
+        /*
          * This is pretty hackish.
          * Casey says that we shouldn't have to do
          * file system specific code, but it does help