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

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

Post by J. Bruce F » Thu, 18 Oct 2007 04:40:13


From: J. Bruce Fields < XXXX@XXXXX.COM >

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 < XXXX@XXXXX.COM >
---
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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[PATCH] dcache: don't expose uninitialized memory in /proc/<pid>/fd/<fd>

Post by J. Bruce F » Wed, 24 Oct 2007 03:10:11

Sorry for the delayed response:




The memcpy() makes the behavior agree with the code comments, and with
what the kernel normally otherwise does. But, yeah, just making it a
null string would probably be reasonable too.


Looks like __d_path already adds a (deleted) for us, so that'de be
redundant.

--b.
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