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

Greg Kroah-Hartman
2014-02-18T23:31:37Z

From: Dan Rosenberg <drosenberg@vsecurity.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@gmail.com>
Signed-off-by: Dan Rosenberg <dan.j.rosenberg@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Li Zefan <lizefan@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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);