linux-kernel - Re: [PATCH] ipc: explicitly clear stack memory in user structs

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Message-ID: <AANLkTi=c4kt46Pa1FA-e8=36Vn0KcmZgHHKWKZ_bgvzL@mail.gmail.com>
Date:	Tue, 9 Nov 2010 22:43:07 +0200
From:	Pekka Enberg <penberg@...nel.org>
To:	Kees Cook <kees.cook@...onical.com>
Cc:	linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	"David S. Miller" <davem@...emloft.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Manfred Spraul <manfred@...orfullife.com>
Subject: Re: [PATCH] ipc: explicitly clear stack memory in user structs

On Tue, Oct 26, 2010 at 2:58 AM, Kees Cook <kees.cook@...onical.com> wrote:
> CVE-2010-4072
>
> The old shm interface will leak a few bytes of stack contents. Explicitly
> clear structure using memset instead of C99-style initialization in case
> there are ever holes in the packing.
>
> Cc: stable <stable@...nel.org>
> Signed-off-by: Kees Cook <kees.cook@...onical.com>

This looks like a genuine bug fix but I don't see this patch in
mainline. Why is that?

> ---
>
> This was originally sent as http://lkml.org/lkml/2010/10/6/486 but was
> never taken into any tree.
>
> ---
>  ipc/shm.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/ipc/shm.c b/ipc/shm.c
> index 52ed77e..f943b1e 100644
> --- a/ipc/shm.c
> +++ b/ipc/shm.c
> @@ -473,6 +473,7 @@ static inline unsigned long copy_shmid_to_user(void __user *buf, struct shmid64_
>            {
>                struct shmid_ds out;
>
> +               memset(&out, 0, sizeof(out));
>                ipc64_perm_to_ipc_perm(&in->shm_perm, &out.shm_perm);
>                out.shm_segsz   = in->shm_segsz;
>                out.shm_atime   = in->shm_atime;
> @@ -524,6 +525,7 @@ static inline unsigned long copy_shminfo_to_user(void __user *buf, struct shminf
>            {
>                struct shminfo out;
>
> +               memset(&out, 0, sizeof(out));
>                if(in->shmmax > INT_MAX)
>                        out.shmmax = INT_MAX;
>                else
> --
> 1.7.1
>
> --
> Kees Cook
> Ubuntu Security Team
> --
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