Patch "lsm: fix smack_inode_removexattr and xattr_getsecurity memleak" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

lsm: fix smack_inode_removexattr and xattr_getsecurity memleak

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
lsm-fix-smack_inode_removexattr-and-xattr_getsecurity-memleak.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Casey Schaufler <[email protected]>
Date: Tue, 19 Sep 2017 09:39:08 -0700
Subject: lsm: fix smack_inode_removexattr and xattr_getsecurity memleak

From: Casey Schaufler <[email protected]>

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.

---
 fs/xattr.c                 |    2 -
 security/smack/smack_lsm.c |   59 ++++++++++++++++++++-------------------------
 2 files changed, 28 insertions(+), 33 deletions(-)

@@ -163,7 +163,7 @@ xattr_getsecurity(struct inode *inode, c
 	}
 	memcpy(value, buffer, len);
 out:
-	security_release_secctx(buffer, len);
+	kfree(buffer);
 out_noalloc:
 	return len;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/lsm-fix-smack_inode_removexattr-and-xattr_getsecurity-memleak.patch