linux-kernel - [PATCH 3.4 23/24] lib/vsprintf.c: kptr_restrict: fix pK-error in SysRq show-all-timers(Q)

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Message-Id: <20140218224550.882493475@linuxfoundation.org>
Date:	Tue, 18 Feb 2014 14:47:10 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Stevie Trujillo <stevie.trujillo@...il.com>,
	Dan Rosenberg <dan.j.rosenberg@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ben Hutchings <ben@...adent.org.uk>,
	Li Zefan <lizefan@...wei.com>
Subject: [PATCH 3.4 23/24] lib/vsprintf.c: kptr_restrict: fix pK-error in SysRq show-all-timers(Q)

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Rosenberg <drosenberg@...curity.com>

commit 3715c5309f6d175c3053672b73fd4f73be16fd07 upstream.

When using 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

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.

Reported-by: Stevie Trujillo <stevie.trujillo@...il.com>
Signed-off-by: Dan Rosenberg <dan.j.rosenberg@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Cc: Li Zefan <lizefan@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 lib/vsprintf.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -926,7 +926,8 @@ char *pointer(const char *fmt, char *buf
 		 * %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 = 2 * sizeof(void *);
 			return string(buf, end, "pK-error", spec);


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