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

["J. Bruce Fields" <bfields@fieldses.org>]

From: J. Bruce Fields <bfields@citi.umich.edu>

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.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
---
 fs/dcache.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

(Am I missing something?  I've also 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>.)

diff --git a/fs/dcache.c b/fs/dcache.c
index 5663a31..24252fc 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1483,6 +1483,8 @@ 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;
 		}
-- 
1.5.3.4.208.gc990

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