[PATCH] mm: fix devision by 0 in percpu_pagelist_fraction

[PATCH] mm: fix devision by 0 in percpu_pagelist_fraction

[Sasha Levin]

percpu_pagelist_fraction_sysctl_handler() has only considered -EINVAL as a possible error
from proc_dointvec_minmax(). If any other error is returned, it would proceed to divide by
zero since percpu_pagelist_fraction wasn't getting initialized at any point. For example,
writing 0 bytes into the proc file would trigger the issue.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
 mm/page_alloc.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1b951de..1e00729 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -106,7 +106,7 @@ unsigned long totalreserve_pages __read_mostly;
  */
 unsigned long dirty_balance_reserve __read_mostly;
 
-int percpu_pagelist_fraction;
+int percpu_pagelist_fraction = 8;
 gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;
 
 #ifdef CONFIG_PM_SLEEP
@@ -5271,7 +5271,7 @@ int percpu_pagelist_fraction_sysctl_handler(ctl_table *table, int write,
 	int ret;
 
 	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
-	if (!write || (ret == -EINVAL))
+	if (!write || (ret < 0))
 		return ret;
 	for_each_populated_zone(zone) {
 		for_each_possible_cpu(cpu) {
-- 
1.7.8.5

[PATCH] mm: fix devision by 0 in percpu_pagelist_fraction

[Sasha Levin]

percpu_pagelist_fraction_sysctl_handler() has only considered -EINVAL as a possible error
from proc_dointvec_minmax(). If any other error is returned, it would proceed to divide by
zero since percpu_pagelist_fraction wasn't getting initialized at any point. For example,
writing 0 bytes into the proc file would trigger the issue.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
 mm/page_alloc.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1b951de..1e00729 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -106,7 +106,7 @@ unsigned long totalreserve_pages __read_mostly;
  */
 unsigned long dirty_balance_reserve __read_mostly;
 
-int percpu_pagelist_fraction;
+int percpu_pagelist_fraction = 8;
 gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;
 
 #ifdef CONFIG_PM_SLEEP
@@ -5271,7 +5271,7 @@ int percpu_pagelist_fraction_sysctl_handler(ctl_table *table, int write,
 	int ret;
 
 	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
-	if (!write || (ret == -EINVAL))
+	if (!write || (ret < 0))
 		return ret;
 	for_each_populated_zone(zone) {
 		for_each_possible_cpu(cpu) {
-- 
1.7.8.5

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Re: [PATCH] mm: fix devision by 0 in percpu_pagelist_fraction

[Minchan Kim]

On 04/28/2012 11:25 PM, Sasha Levin wrote:

> percpu_pagelist_fraction_sysctl_handler() has only considered -EINVAL as a possible error
> from proc_dointvec_minmax(). If any other error is returned, it would proceed to divide by
> zero since percpu_pagelist_fraction wasn't getting initialized at any point. For example,
> writing 0 bytes into the proc file would trigger the issue.
> 
> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>


Reviewed-by: Minchan Kim <minchan@kernel.org>

-- 
Kind regards,
Minchan Kim

Re: [PATCH] mm: fix devision by 0 in percpu_pagelist_fraction

[Minchan Kim]

On 04/28/2012 11:25 PM, Sasha Levin wrote:

> percpu_pagelist_fraction_sysctl_handler() has only considered -EINVAL as a possible error
> from proc_dointvec_minmax(). If any other error is returned, it would proceed to divide by
> zero since percpu_pagelist_fraction wasn't getting initialized at any point. For example,
> writing 0 bytes into the proc file would trigger the issue.
> 
> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>


Reviewed-by: Minchan Kim <minchan@kernel.org>

-- 
Kind regards,
Minchan Kim

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