From: Andrew Morton <akpm@linux-foundation.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 1/2] binfmt_elf: Fix corner case kfree of uninitialized data
Date: Wed, 26 Sep 2012 16:21:51 -0700 [thread overview]
Message-ID: <20120926162151.ef9a552d.akpm@linux-foundation.org> (raw)
In-Reply-To: <20120919144410.16893.57933.stgit@localhost.localdomain>
On Wed, 19 Sep 2012 15:44:35 +0100
Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> Could do with double checking...
>
> From: Alan Cox <alan@linux.intel.com>
>
> If elf_core_dump is called and fill_note_info fails in the kmalloc then
> it returns 0 but has not yet initialised all the needed fields. As a result
> we do a kfree(randomness) after correctly skipping the thread data.
>
> Signed-off-by: Alan Cox <alan@linux.intel.com>
> ---
>
> fs/binfmt_elf.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index 1b4efbc..bf6d82b 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -1492,8 +1492,10 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
> info->thread = NULL;
>
> psinfo = kmalloc(sizeof(*psinfo), GFP_KERNEL);
> - if (psinfo == NULL)
> + if (psinfo == NULL) {
> + info->psinfo.data = NULL; /* So we don't free this wrongly */
> return 0;
> + }
>
> fill_note(&info->psinfo, "CORE", NT_PRPSINFO, sizeof(*psinfo), psinfo);
afaict it's NotABug, because fill_note_info() does
info->thread = NULL;
psinfo = kmalloc(sizeof(*psinfo), GFP_KERNEL);
if (psinfo == NULL) {
and free_note_info() does
struct elf_thread_core_info *threads = info->thread;
while (threads) {
so free_note_info() won't enter the freeing loop at all.
Which is just as well, because info->thread_notes is uninitialised at
this time.
It all looks rather fragile - I'm wondering if it would be sanest to
memset `info' right at the outset in elf_core_dump(), then weed out all
the now-unneeded zeroizings in fill_note_info().
Also, how irritating is it that fill_note_info() has a local var
`psinfo' which has a different type from info->psinfo. That had me
running around for a while...
prev parent reply other threads:[~2012-09-26 23:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-19 14:44 [RFC PATCH 1/2] binfmt_elf: Fix corner case kfree of uninitialized data Alan Cox
2012-09-19 14:45 ` [RFC PATCH 2/2] binfmt_elf: Uninitialized variable Alan Cox
2012-09-26 23:25 ` Andrew Morton
2012-09-26 23:21 ` Andrew Morton [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20120926162151.ef9a552d.akpm@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=alan@lxorguk.ukuu.org.uk \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).