Fwd: [PATCH] ARM: Fix restoration of IP scratch register when auditing syscalls

[Josh Boyer]

On Sun, Apr 29, 2012 at 02:40:01AM -0400, Jon Masters wrote:
> 
> 
> -------- Original Message --------
> Subject: [PATCH] ARM: Fix restoration of IP scratch register when
> auditing syscalls
> Date: Sun, 29 Apr 2012 02:38:24 -0400
> From: Jon Masters <jcm at jonmasters.org>
> To: Linux ARM Kernel <linux-arm-kernel at lists.infradead.org>
> CC: Jon Masters <jcm at redhat.com>, Al Viro <viro at zeniv.linux.org.uk>,
>     Eric Paris <eparis at redhat.com>, Jon Masters <jcm at jonmasters.org>
> 
> The audit subsystem builds upon ptrace to record system calls. This is done
> in a couple of places (on return from fork into a new task, on exit from
> the SWI vector), using calls to syscall_trace. The latter function abuses
> the userspace intra-procedure scratch register (regs->ARM_ip, aka r12),
> and intends to restore it prior to return to userspace. Unfortunately,
> there are cases where we will return to userspace without restoring.
> 
> If we are in fact not ptracing but are merely auditing calls, we will
> happily trash the content of ip but will exit to userspace without
> restoring the value. It just so happens that GLIBC uses ip as a
> storage for the TLS thread pointer info, and bad things result.
> 
> The fix is simply to have an additional out when not ptracing.
> 
> Signed-off-by: Jon Masters <jcm at jonmasters.org>
> ---

Going to assume you forwarded this here because you want it applied to
the Fedora kernel.  Likely F17/rawhide?

I'm guessing we probably want to follow
http://lists.infradead.org/pipermail/linux-arm-kernel/2012-April/096951.html
for a bit to see if there are any more iterations of this?

Since it's CC'd to stable, it should get picked up rather quickly if RMK
applies it.

josh