linux-kernel - [PATCH] mm: vmscan: add BUG_ON on illegal return values from scan

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Date:	Mon, 20 May 2013 11:14:27 +0200
From:	Oskar Andero <oskar.andero@...ymobile.com>
To:	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
CC:	Radovan Lekanovic <radovan.lekanovic@...ymobile.com>,
	David Rientjes <rientjes@...gle.com>,
	Oskar Andero <oskar.andero@...ymobile.com>,
	Glauber Costa <glommer@...nvz.org>,
	Dave Chinner <dchinner@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH] mm: vmscan: add BUG_ON on illegal return values from scan_objects

Add a BUG_ON to catch any illegal value from the shrinkers. This fixes a
potential bug if scan_objects returns a negative other than -1, which
would lead to undefined behaviour.

Cc: Glauber Costa <glommer@...nvz.org>
Cc: Dave Chinner <dchinner@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Oskar Andero <oskar.andero@...ymobile.com>
---
 mm/vmscan.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6bac41e..fbe6742 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -293,6 +293,7 @@ shrink_slab_one(struct shrinker *shrinker, struct shrink_control *shrinkctl,
 		ret = shrinker->scan_objects(shrinker, shrinkctl);
 		if (ret == -1)
 			break;
+		BUG_ON(ret < -1);
 		freed += ret;
 
 		count_vm_events(SLABS_SCANNED, nr_to_scan);
-- 
1.8.1.5

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