linux-kernel - Re: kptr_restrict: pK-error in SysRq show-all-timers(Q)

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Date:	Fri, 13 Jul 2012 19:22:31 -0400
From:	Dan Rosenberg <drosenberg@...curity.com>
To:	Stevie Trujillo <stevie.trujillo@...il.com>
CC:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: kptr_restrict: pK-error in SysRq show-all-timers(Q)

On 06/26/2012 05:20 PM, Stevie Trujillo wrote:
> Hello,
>
> if I press ALT+SysRq+Q all the pointers are replaced with "pK-error" like this:
> [23153.208033]   .base:               pK-error
>
> with echo h > /proc/sysrq-trigger it works:
> [23107.776363]   .base:       ffff88023e60d540
>
> --
> Stevie Trujillo

The intent behind this behavior was to return "pK-error" in cases where the %pK
format specifier was used in interrupt context, because the CAP_SYSLOG check
wouldn't be meaningful.  Clearly this should only apply when kptr_restrict is
actually enabled though.

Signed-off-by: Dan Rosenberg <dan.j.rosenberg@...il.com>
Cc: stable@...r.kernel.org
---
 lib/vsprintf.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index c3f36d41..598a73e 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1030,7 +1030,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 		 * %pK cannot be used in IRQ context because its test
 		 * for CAP_SYSLOG would be meaningless.
 		 */
-		if (in_irq() || in_serving_softirq() || in_nmi()) {
+		if (kptr_restrict && (in_irq() || in_serving_softirq() ||
+				      in_nmi())) {
 			if (spec.field_width == -1)
 				spec.field_width = default_width;
 			return string(buf, end, "pK-error", spec);

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