This is a note to let you know that I've just added the patch titled
mm/page-writeback.c: fix divide by zero in pos_ratio_polynom
to the 3.14-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:
mm-page-writeback.c-fix-divide-by-zero-in-pos_ratio_polynom.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d5c9fde3dae750889168807038243ff36431d276 Mon Sep 17 00:00:00 2001
From: Rik van Riel <riel@xxxxxxxxxx>
Date: Tue, 6 May 2014 12:50:01 -0700
Subject: mm/page-writeback.c: fix divide by zero in pos_ratio_polynom
From: Rik van Riel <riel@xxxxxxxxxx>
commit d5c9fde3dae750889168807038243ff36431d276 upstream.
It is possible for "limit - setpoint + 1" to equal zero, after getting
truncated to a 32 bit variable, and resulting in a divide by zero error.
Using the fully 64 bit divide functions avoids this problem. It also
will cause pos_ratio_polynom() to return the correct value when
(setpoint - limit) exceeds 2^32.
Also uninline pos_ratio_polynom, at Andrew's request.
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Nishanth Aravamudan <nacc@xxxxxxxxxxxxxxxxxx>
Cc: Luiz Capitulino <lcapitulino@xxxxxxxxxx>
Cc: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/page-writeback.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -593,14 +593,14 @@ unsigned long bdi_dirty_limit(struct bac
* (5) the closer to setpoint, the smaller |df/dx| (and the reverse)
* => fast response on large errors; small oscillation near setpoint
*/
-static inline long long pos_ratio_polynom(unsigned long setpoint,
+static long long pos_ratio_polynom(unsigned long setpoint,
unsigned long dirty,
unsigned long limit)
{
long long pos_ratio;
long x;
- x = div_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT,
+ x = div64_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT,
limit - setpoint + 1);
pos_ratio = x;
pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT;
@@ -842,7 +842,7 @@ static unsigned long bdi_position_ratio(
x_intercept = bdi_setpoint + span;
if (bdi_dirty < x_intercept - span / 4) {
- pos_ratio = div_u64(pos_ratio * (x_intercept - bdi_dirty),
+ pos_ratio = div64_u64(pos_ratio * (x_intercept - bdi_dirty),
x_intercept - bdi_setpoint + 1);
} else
pos_ratio /= 4;
Patches currently in stable-queue which might be from riel@xxxxxxxxxx are
queue-3.14/revert-mm-vmscan-do-not-swap-anon-pages-just-because-free-file-is-low.patch
queue-3.14/mm-thp-close-race-between-mremap-and-split_huge_page.patch
queue-3.14/mm-compaction-make-isolate_freepages-start-at-pageblock-boundary.patch
queue-3.14/mm-page-writeback.c-fix-divide-by-zero-in-pos_ratio_polynom.patch
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