lsm: fix smack_inode_removexattr and xattr_getsecurity memleak

commit 57e7ba04d422c3d41c8426380303ec9b7533ded9 upstream.

security_inode_getsecurity() provides the text string value
of a security attribute. It does not provide a "secctx".
The code in xattr_getsecurity() that calls security_inode_getsecurity()
and then calls security_release_secctx() happened to work because
SElinux and Smack treat the attribute and the secctx the same way.
It fails for cap_inode_getsecurity(), because that module has no
secctx that ever needs releasing. It turns out that Smack is the
one that's doing things wrong by not allocating memory when instructed
to do so by the "alloc" parameter.

The fix is simple enough. Change the security_release_secctx() to
kfree() because it isn't a secctx being returned by
security_inode_getsecurity(). Change Smack to allocate the string when
told to do so.

Note: this also fixes memory leaks for LSMs which implement
inode_getsecurity but not release_secctx, such as capabilities.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reported-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: James Morris <james.l.morris@oracle.com>
[bwh: Backported to 3.2:
 - s/isp->smk_known/isp/
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/xattr.c b/fs/xattr.c
index 67583de8218cf54213379f586926824f30da5350..f91e3c1d57a922ef57dc15b23d48900a6fb64949 100644 (file)
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -161,7 +161,7 @@ xattr_getsecurity(struct inode *inode, const char *name, void *value,
        }
        memcpy(value, buffer, len);
 out:
-       security_release_secctx(buffer, len);
+       kfree(buffer);
 out_noalloc:
        return len;
 }

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 7051499332f6fb0370be90fa10b43751bd805349..5e23bb80556e951bc15974737bc2190187899e8f 100644 (file)
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -940,7 +940,7 @@ static int smack_inode_removexattr(struct dentry *dentry, const char *name)
  * @inode: the object
  * @name: attribute name
  * @buffer: where to put the result
- * @alloc: unused
+ * @alloc: duplicate memory
  *
  * Returns the size of the attribute or an error code
  */
@@ -953,43 +953,38 @@ static int smack_inode_getsecurity(const struct inode *inode,
        struct super_block *sbp;
        struct inode *ip = (struct inode *)inode;
        char *isp;
-       int ilen;
-       int rc = 0;
 
-       if (strcmp(name, XATTR_SMACK_SUFFIX) == 0) {
+       if (strcmp(name, XATTR_SMACK_SUFFIX) == 0)
                isp = smk_of_inode(inode);
-               ilen = strlen(isp);
-               *buffer = isp;
-               return ilen;
-       }
+       else {
+               /*
+                * The rest of the Smack xattrs are only on sockets.
+                */
+               sbp = ip->i_sb;
+               if (sbp->s_magic != SOCKFS_MAGIC)
+                       return -EOPNOTSUPP;
 
-       /*
-        * The rest of the Smack xattrs are only on sockets.
-        */
-       sbp = ip->i_sb;
-       if (sbp->s_magic != SOCKFS_MAGIC)
-               return -EOPNOTSUPP;
+               sock = SOCKET_I(ip);
+               if (sock == NULL || sock->sk == NULL)
+                       return -EOPNOTSUPP;
 
-       sock = SOCKET_I(ip);
-       if (sock == NULL || sock->sk == NULL)
-               return -EOPNOTSUPP;
-
-       ssp = sock->sk->sk_security;
+               ssp = sock->sk->sk_security;
 
-       if (strcmp(name, XATTR_SMACK_IPIN) == 0)
-               isp = ssp->smk_in;
-       else if (strcmp(name, XATTR_SMACK_IPOUT) == 0)
-               isp = ssp->smk_out;
-       else
-               return -EOPNOTSUPP;
+               if (strcmp(name, XATTR_SMACK_IPIN) == 0)
+                       isp = ssp->smk_in;
+               else if (strcmp(name, XATTR_SMACK_IPOUT) == 0)
+                       isp = ssp->smk_out;
+               else
+                       return -EOPNOTSUPP;
+       }
 
-       ilen = strlen(isp);
-       if (rc == 0) {
-               *buffer = isp;
-               rc = ilen;
+       if (alloc) {
+               *buffer = kstrdup(isp, GFP_KERNEL);
+               if (*buffer == NULL)
+                       return -ENOMEM;
        }
 
-       return rc;
+       return strlen(isp);
 }