Commit edce6820 authored Aug 30, 2010 by Jeffrey Carlyle Committed by Jens Axboe Aug 30, 2010

scatterlist: prevent invalid free when alloc fails



When alloc fails, free_table is being called. Depending on the number of
bytes requested, we determine if we are going to call _get_free_page()
or kmalloc(). When alloc fails, our math is wrong (due to sg_size - 1),
and the last buffer is wrongfully assumed to have been allocated by
kmalloc. Hence, kfree gets called and a panic occurs.

Signed-off-by: Jeffrey Carlyle <jeff.carlyle@motorola.com>
Signed-off-by: Olusanya Soyannwo <c23746@motorola.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

parent b76b4014

lib/scatterlist.c

+12 −2

Original line number	Original line	Diff line number	Diff line
	@@ -248,8 +248,18 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents,
	left -= sg_size;		left -= sg_size;

	sg = alloc_fn(alloc_size, gfp_mask);		sg = alloc_fn(alloc_size, gfp_mask);
	if (unlikely(!sg))		if (unlikely(!sg)) {
			/*
			* Adjust entry count to reflect that the last
			* entry of the previous table won't be used for
			* linkage. Without this, sg_kfree() may get
			* confused.
			*/
			if (prv)
			table->nents = ++table->orig_nents;

	return -ENOMEM;		return -ENOMEM;
			}

	sg_init_table(sg, alloc_size);		sg_init_table(sg, alloc_size);
	table->nents = table->orig_nents += sg_size;		table->nents = table->orig_nents += sg_size;

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