linux-kernel - [PATCH] fs: Fix theoretical division by 0 in super_cache

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <201405172102.GII52606.JtMOQOOFVHFLFS@I-love.SAKURA.ne.jp>
Date:	Sat, 17 May 2014 21:02:42 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	linux-fsdevel@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] fs: Fix theoretical division by 0 in super_cache_scan().

>>From 7a2ed4e9c91864736ce5ad89489fd5862d59542e Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Date: Sat, 17 May 2014 20:56:38 +0900
Subject: [PATCH] fs: Fix theoretical division by 0 in super_cache_scan().

total_objects could be 0 and is used as a denom.

While total_objects is a "long", total_objects == 0 unlikely happens for
3.12 and later kernels because 32-bit architectures would not be able to
hold (1 << 32) objects. However, total_objects == 0 may happen for kernels
between 3.1 and 3.11 because total_objects in prune_super() was an "int"
and (e.g.) x86_64 architecture might be able to hold (1 << 32) objects.

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc: stable <stable@...nel.org> # 3.1+
---
 fs/super.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/super.c b/fs/super.c
index 48377f7..1408362 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -81,6 +81,8 @@ static unsigned long super_cache_scan(struct shrinker *shrink,
 	inodes = list_lru_count_node(&sb->s_inode_lru, sc->nid);
 	dentries = list_lru_count_node(&sb->s_dentry_lru, sc->nid);
 	total_objects = dentries + inodes + fs_objects + 1;
+	if (!total_objects)
+		total_objects = 1;

 	/* proportion the scan between the caches */
 	dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);
-- 
1.7.1
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/