This is a note to let you know that I've just added the patch titled
timekeeping: Cap array access in timekeeping_debug
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
timekeeping-cap-array-access-in-timekeeping_debug.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a4f8f6667f099036c88f231dcad4cf233652c824 Mon Sep 17 00:00:00 2001
From: John Stultz <john.stultz@xxxxxxxxxx>
Date: Tue, 23 Aug 2016 16:08:22 -0700
Subject: timekeeping: Cap array access in timekeeping_debug
From: John Stultz <john.stultz@xxxxxxxxxx>
commit a4f8f6667f099036c88f231dcad4cf233652c824 upstream.
It was reported that hibernation could fail on the 2nd attempt, where the
system hangs at hibernate() -> syscore_resume() -> i8237A_resume() ->
claim_dma_lock(), because the lock has already been taken.
However there is actually no other process would like to grab this lock on
that problematic platform.
Further investigation showed that the problem is triggered by setting
/sys/power/pm_trace to 1 before the 1st hibernation.
Since once pm_trace is enabled, the rtc becomes unmeaningful after suspend,
and meanwhile some BIOSes would like to adjust the 'invalid' RTC (e.g, smaller
than 1970) to the release date of that motherboard during POST stage, thus
after resumed, it may seem that the system had a significant long sleep time
which is a completely meaningless value.
Then in timekeeping_resume -> tk_debug_account_sleep_time, if the bit31 of the
sleep time happened to be set to 1, fls() returns 32 and we add 1 to
sleep_time_bin[32], which causes an out of bounds array access and therefor
memory being overwritten.
As depicted by System.map:
0xffffffff81c9d080 b sleep_time_bin
0xffffffff81c9d100 B dma_spin_lock
the dma_spin_lock.val is set to 1, which caused this problem.
This patch adds a sanity check in tk_debug_account_sleep_time()
to ensure we don't index past the sleep_time_bin array.
[jstultz: Problem diagnosed and original patch by Chen Yu, I've solved the
issue slightly differently, but borrowed his excelent explanation of the
issue here.]
Fixes: 5c83545f24ab "power: Add option to log time spent in suspend"
Reported-by: Janek Kozicki <cosurgi@xxxxxxxxx>
Reported-by: Chen Yu <yu.c.chen@xxxxxxxxx>
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
Cc: linux-pm@xxxxxxxxxxxxxxx
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Xunlei Pang <xpang@xxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Cc: Zhang Rui <rui.zhang@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1471993702-29148-3-git-send-email-john.stultz@xxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/time/timekeeping_debug.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/kernel/time/timekeeping_debug.c
+++ b/kernel/time/timekeeping_debug.c
@@ -23,7 +23,9 @@
#include "timekeeping_internal.h"
-static unsigned int sleep_time_bin[32] = {0};
+#define NUM_BINS 32
+
+static unsigned int sleep_time_bin[NUM_BINS] = {0};
static int tk_debug_show_sleep_time(struct seq_file *s, void *data)
{
@@ -69,6 +71,9 @@ late_initcall(tk_debug_sleep_time_init);
void tk_debug_account_sleep_time(struct timespec64 *t)
{
- sleep_time_bin[fls(t->tv_sec)]++;
+ /* Cap bin index so we don't overflow the array */
+ int bin = min(fls(t->tv_sec), NUM_BINS-1);
+
+ sleep_time_bin[bin]++;
}
Patches currently in stable-queue which might be from john.stultz@xxxxxxxxxx are
queue-4.4/0110-ntp-Fix-ADJ_SETOFFSET-being-used-w-ADJ_NANO.patch
queue-4.4/timekeeping-avoid-taking-lock-in-nmi-path-with-config_debug_timekeeping.patch
queue-4.4/0109-time-Verify-time-values-in-adjtimex-ADJ_SETOFFSET-to.patch
queue-4.4/0118-clocksource-Allow-unregistering-the-watchdog.patch
queue-4.4/timekeeping-cap-array-access-in-timekeeping_debug.patch
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