From edce6820a9fdda85521211cb334a183e34cc455e Mon Sep 17 00:00:00 2001 From: Jeffrey Carlyle Date: Mon, 30 Aug 2010 19:55:09 +0200 Subject: [PATCH] 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 Signed-off-by: Olusanya Soyannwo Acked-by: Tejun Heo Signed-off-by: Jens Axboe --- lib/scatterlist.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/lib/scatterlist.c b/lib/scatterlist.c index a5ec42868f99..4ceb05d772ae 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -248,8 +248,18 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents, left -= sg_size; sg = alloc_fn(alloc_size, gfp_mask); - if (unlikely(!sg)) - return -ENOMEM; + 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; + } sg_init_table(sg, alloc_size); table->nents = table->orig_nents += sg_size;