lkml.org 
[lkml]   [2010]   [Aug]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] scatterlist: prevent invalid free when alloc fails
Hello,

First of all, the patch is line-wrapped. Please check your email
settings.

On 08/26/2010 06:04 PM, Jeffrey Carlyle wrote:
> 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.
>
> This fix sets the end marker and allows the proper freeing of the
> buffers.
>
> Signed-off-by: Olusanya Soyannwo <c23746@motorola.com>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Jens Axboe <jaxboe@fusionio.com>
> Signed-off-by: Jeffrey Carlyle <jeff.carlyle@motorola.com>
> ---
> lib/scatterlist.c | 11 +++++++++--
> 1 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/lib/scatterlist.c b/lib/scatterlist.c
> index a5ec428..acf2c6e 100644
> --- a/lib/scatterlist.c
> +++ b/lib/scatterlist.c
> @@ -163,7 +163,7 @@ void __sg_free_table(struct sg_table *table,
> unsigned int max_ents,
> return;
>
> sgl = table->sgl;
> - while (table->orig_nents) {
> + while (table->orig_nents && sgl) {
> unsigned int alloc_size = table->orig_nents;
> unsigned int sg_size;

Why is this change necessary?

> @@ -227,6 +227,7 @@ int __sg_alloc_table(struct sg_table *table,
> unsigned int nents,
> {
> struct scatterlist *sg, *prv;
> unsigned int left;
> + unsigned int total_alloc = 0;
>
> #ifndef ARCH_HAS_SG_CHAIN
> BUG_ON(nents > max_ents);
> @@ -248,8 +249,14 @@ int __sg_alloc_table(struct sg_table *table,
> unsigned int nents,
> left -= sg_size;
>
> sg = alloc_fn(alloc_size, gfp_mask);
> - if (unlikely(!sg))
> + if (unlikely(!sg)) {
> + table->orig_nents = total_alloc;
> + /* mark the end of previous entry */
> + sg_mark_end(&prv[alloc_size - 1]);

prv[alloc_size - 1] is already marked as end by sg_init_table() during
the previous iteration. Also, prv can be NULL at this point. AFAICS,
the only thing necessary would be "if (prv) table->nents++", no?

Thanks.

--
tejun


\
 
 \ /
  Last update: 2010-08-27 12:27    [W:0.114 / U:21.384 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site