VFS/Security: Rework inode_getsecurity and callers to return resulting buffer

This patch modifies the interface to inode_getsecurity to have the function
return a buffer containing the security blob and its length via parameters
instead of relying on the calling function to give it an appropriately sized
buffer.

Security blobs obtained with this function should be freed using the
release_secctx LSM hook.  This alleviates the problem of the caller having to
guess a length and preallocate a buffer for this function allowing it to be
used elsewhere for Labeled NFS.

The patch also removed the unused err parameter.  The conversion is similar to
the one performed by Al Viro for the security_getprocattr hook.

Signed-off-by: David P. Quigley <dpquigl@tycho.nsa.gov>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Chris Wright <chrisw@sous-sol.org>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 2 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index ee9024483f60..0f246c44a574 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1955,8 +1955,7 @@ static int shmem_xattr_security_get(struct inode *inode, const char *name,
 {
         if (strcmp(name, "") == 0)
                 return -EINVAL;
-        return security_inode_getsecurity(inode, name, buffer, size,
-                                          -EOPNOTSUPP);
+        return xattr_getsecurity(inode, name, buffer, size);
 }
 
 static int shmem_xattr_security_set(struct inode *inode, const char *name,