From: J. Bruce Fields <bfields@citi.umich.edu>
Date: Sun, 21 Oct 2007 23:41:38 +0000 (-0700)
Subject: dcache: don't expose uninitialized memory in /proc/<pid>/fd/<fd>
X-Git-Tag: firefly_0821_release~24721
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=321bcf92163038e2b96fd3bf9bc29f755c81d9ef;p=firefly-linux-kernel-4.4.55.git

dcache: don't expose uninitialized memory in /proc/<pid>/fd/<fd>

Well, it's not especially important that target->d_iname get the contents
of dentry->d_iname, but it's important that it get initialized with
*something*, otherwise we're just exposing some random piece of memory to
anyone who reads the link at /proc/<pid>/fd/<fd> for the deleted file, when
it's still held open by someone.

I've run a test program that copies a short (<36 character) name ontop of a
long (>=36 character) name and see that the first time I run it, without
this patch, I get unpredicatable results out of /proc/<pid>/fd/<fd>.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
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>
---

diff --git a/fs/dcache.c b/fs/dcache.c
index 2bb3f7ac683b..d9ca1e5ceb92 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1479,6 +1479,8 @@ static void switch_names(struct dentry *dentry, struct dentry *target)
 			 * dentry:internal, target:external.  Steal target's
 			 * storage and make target internal.
 			 */
+			memcpy(target->d_iname, dentry->d_name.name,
+					dentry->d_name.len + 1);
 			dentry->d_name.name = target->d_name.name;
 			target->d_name.name = target->d_iname;
 		}