From 91b57191cfd152c02ded0745250167d0263084f8 Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Tue, 2 Dec 2014 15:59:28 -0800 Subject: [PATCH] mm/vmpressure.c: fix race in vmpressure_work_fn() In some android devices, there will be a "divide by zero" exception. vmpr->scanned could be zero before spin_lock(&vmpr->sr_lock). Addresses https://bugzilla.kernel.org/show_bug.cgi?id=88051 [akpm@linux-foundation.org: neaten] Reported-by: ji_ang Cc: Anton Vorontsov Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmpressure.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/vmpressure.c b/mm/vmpressure.c index d4042e75f7c7..c5afd573d7da 100644 --- a/mm/vmpressure.c +++ b/mm/vmpressure.c @@ -165,6 +165,7 @@ static void vmpressure_work_fn(struct work_struct *work) unsigned long scanned; unsigned long reclaimed; + spin_lock(&vmpr->sr_lock); /* * Several contexts might be calling vmpressure(), so it is * possible that the work was rescheduled again before the old @@ -173,11 +174,12 @@ static void vmpressure_work_fn(struct work_struct *work) * here. No need for any locks here since we don't care if * vmpr->reclaimed is in sync. */ - if (!vmpr->scanned) + scanned = vmpr->scanned; + if (!scanned) { + spin_unlock(&vmpr->sr_lock); return; + } - spin_lock(&vmpr->sr_lock); - scanned = vmpr->scanned; reclaimed = vmpr->reclaimed; vmpr->scanned = 0; vmpr->reclaimed = 0; -- 2.20.1