Commit 93278814 authored May 10, 2012 by Sasha Levin Committed by Linus Torvalds May 10, 2012

mm: fix division by 0 in percpu_pagelist_fraction()



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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 16fbdce6

mm/page_alloc.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -105,7 +105,7 @@ 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
		@@ -5203,7 +5203,7 @@ 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) {

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