[lucid/fsl-imx51,maverick/ti-omap4,natty/ti-omap4] proc: fix oops on invalid /proc/<pid>/maps access, CVE-2011-1020

From: Linus Torvalds <torvalds@linux-foundation.org>

When m_start returns an error, the seq_file logic will still call m_stop
with that error entry, so we'd better make sure that we check it before
using it as a vma.

Introduced by commit ec6fd8a4355c ("report errors in /proc/*/*map*
sanely"), which replaced NULL with various ERR_PTR() cases.

(On ia64, you happen to get a unaligned fault instead of a page fault,
since the address used is generally some random error code like -EPERM)

Reported-by: Anca Emanuel <anca.emanuel@gmail.com>
Reported-by: Tony Luck <tony.luck@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Américo Wang <xiyou.wangcong@gmail.com>
Cc: Stephen Wilson <wilsons@start.ca>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 76597cd31470fa130784c78fadb4dab2e624a723)
CVE-2011-1020
BugLink: http://bugs.launchpad.net/bugs/813026
Signed-off-by: Herton R. Krzesinski <herton.krzesinski@canonical.com>

---
 fs/proc/task_mmu.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

This is already applied on lucid, maverick and natty master/master-next,
but is required also on lucid/fsl-imx51, maverick/ti-omap4,
natty/ti-omap4

On 08/29/2011 09:11 AM, Herton R. Krzesinski wrote:
> From: Linus Torvalds<torvalds@linux-foundation.org>
>
> When m_start returns an error, the seq_file logic will still call m_stop
> with that error entry, so we'd better make sure that we check it before
> using it as a vma.
>
> Introduced by commit ec6fd8a4355c ("report errors in /proc/*/*map*
> sanely"), which replaced NULL with various ERR_PTR() cases.
>
> (On ia64, you happen to get a unaligned fault instead of a page fault,
> since the address used is generally some random error code like -EPERM)
>
> Reported-by: Anca Emanuel<anca.emanuel@gmail.com>
> Reported-by: Tony Luck<tony.luck@intel.com>
> Cc: Al Viro<viro@zeniv.linux.org.uk>
> Cc: Américo Wang<xiyou.wangcong@gmail.com>
> Cc: Stephen Wilson<wilsons@start.ca>
> Signed-off-by: Linus Torvalds<torvalds@linux-foundation.org>
> (cherry picked from commit 76597cd31470fa130784c78fadb4dab2e624a723)
> CVE-2011-1020
> BugLink: http://bugs.launchpad.net/bugs/813026
> Signed-off-by: Herton R. Krzesinski<herton.krzesinski@canonical.com>
>
> ---
>   fs/proc/task_mmu.c |    3 ++-
>   1 files changed, 2 insertions(+), 1 deletions(-)
>
> This is already applied on lucid, maverick and natty master/master-next,
> but is required also on lucid/fsl-imx51, maverick/ti-omap4,
> natty/ti-omap4
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 7c708a4..2e7addf 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -182,7 +182,8 @@ static void m_stop(struct seq_file *m, void *v)
>   	struct proc_maps_private *priv = m->private;
>   	struct vm_area_struct *vma = v;
>
> -	vma_stop(priv, vma);
> +	if (!IS_ERR(vma))
> +		vma_stop(priv, vma);
>   	if (priv->task)
>   		put_task_struct(priv->task);
>   }