Commit 475d0db7 authored May 17, 2014 by Tetsuo Handa Committed by Al Viro Oct 09, 2014

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@I-love.SAKURA.ne.jp>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: stable <stable@kernel.org> # 3.1+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

parent b8314f93

fs/super.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -80,6 +80,8 @@ 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);

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