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From: Mark Johnston <markj@FreeBSD.org>
Date: Fri, 12 Feb 2016 20:43:53 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r295574 - head/sys/fs/tmpfs
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Author: markj
Date: Fri Feb 12 20:43:53 2016
New Revision: 295574
URL: https://svnweb.freebsd.org/changeset/base/295574

Log:
  Clear the cookie pointer on error in tmpfs_readdir().
  
  It is otherwise left dangling, and callers that request cookies always free
  the cookie buffer, even when VOP_READDIR(9) returns an error. This results
  in a double free if tmpfs_readdir() returns an error to the NFS server or
  the Linux getdents(2) emulation code.
  
  Reported by:	pho
  MFC after:	1 week
  Security:	double free of malloc(9)-backed memory
  Sponsored by:	EMC / Isilon Storage Division

Modified:
  head/sys/fs/tmpfs/tmpfs_vnops.c

Modified: head/sys/fs/tmpfs/tmpfs_vnops.c
==============================================================================
--- head/sys/fs/tmpfs/tmpfs_vnops.c	Fri Feb 12 20:14:03 2016	(r295573)
+++ head/sys/fs/tmpfs/tmpfs_vnops.c	Fri Feb 12 20:43:53 2016	(r295574)
@@ -1191,8 +1191,11 @@ tmpfs_readdir(struct vop_readdir_args *v
 	if (error == EJUSTRETURN)
 		error = (uio->uio_resid != startresid) ? 0 : EINVAL;
 
-	if (error != 0 && cookies != NULL)
+	if (error != 0 && cookies != NULL && ncookies != NULL) {
 		free(*cookies, M_TEMP);
+		*cookies = NULL;
+		*ncookies = 0;
+	}
 
 	if (eofflag != NULL)
 		*eofflag =