Re: [PATCH] dcache: don't expose uninitialized memory in /proc//fd/

Andrew Morton
2007-10-17T22:32:36Z

On Tue, 16 Oct 2007 15:35:57 -0400
"J. Bruce Fields" <bfields@fieldses.org> wrote:

> 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.
>

hm, that was tricky.

> ---
> 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;
> }

Or we could just stick a \0 in there.

Or perhaps we should set it to "(deleted file)"?