From: Kees Cook <kees.cook@canonical.com>

While mm->start_stack was protected from cross-uid viewing (commit
f83ce3e6b02d5 ("proc: avoid information leaks to non-privileged
processes")), the start_code and end_code values were not. This would
allow the text location of a PIE binary to leak, defeating ASLR.

Note that the value "1" is used instead of "0" for a protected value since
"ps", "killall", and likely other readers of /proc/pid/stat, take
start_code of "0" to mean a kernel thread and will misbehave. Thanks to
Brad Spengler for pointing this out.

Addresses CVE-2011-0726

Signed-off-by: Kees Cook <kees.cook@canonical.com>
Cc: <stable@kernel.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Eugene Teo <eugeneteo@kernel.sg>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Brad Spengler <spender@grsecurity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

(cherry picked from commit 5883f57ca0008ffc93e09cbb9847a1928e50c6f3)
CVE-2011-0726
BugLink: http://bugs.launchpad.net/bugs/799906
Signed-off-by: Andy Whitcroft <apw@canonical.com>
---
fs/proc/array.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 725a650..98785b7 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -479,8 +479,8 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
vsize,
mm ? get_mm_rss(mm) : 0,
rsslim,
- mm ? mm->start_code : 0,
- mm ? mm->end_code : 0,
+ mm ? (permitted ? mm->start_code : 1) : 0,
+ mm ? (permitted ? mm->end_code : 1) : 0,
(permitted && mm) ? mm->start_stack : 0,
esp,
eip,
--
1.7.4.1


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On 21.06.2011 11:35, Andy Whitcroft wrote:
> CVE-2011-0726
> ASLR leak in /proc/pid/stat for mm start_code
>
> This has hit Lucid and later via mainline/upstream stable. This needed
> for Hardy, Lucid/fsl-imx51, and Maverick/ti-omap4. Note that for Hardy
> an additional pre-requisite commit is required which also seems to fix
> a number of related ASLR leaks in the same file.
>
> Proposing for Hardy, Lucid/fsl-im51, and Maverick/ti-omap4.
>
> -apw
>

For other (non-Hardy) the patch looks reasonable and according to the descriptions.
Hardy (64bit) was tested running as dom0 and was behaving as expected. The
qa-regression tests passed and it was still possible to launch a domU.

Acked-by: Stefan Bader <stefan.bader@canonical.com>

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