RE: [PATCH] spi: Fix per-page mapping of unaligned vmalloc-ed buffer

[Andrew Gabbasov <andrew_gabbasov-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org>]

> -----Original Message-----
> From: Gabbasov, Andrew
> Sent: Monday, June 15, 2015 9:59 AM
> To: linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> Subject: [PATCH] spi: Fix per-page mapping of unaligned vmalloc-ed buffer
> 
> spi_map_buf() processes mapping of vmalloc-ed buffers in a special way,
making
> mapping of every page separately. However, if the buffer is not aligned to
page
> boundary (e.g. sub-array in a vmalloc-ed array), it fills the scatter
table with
> page-size unaligned pieces, that cross page boundaries. This is incorrect
and
> can, for example, cause memory corruption and various crashes when working
> with ubifs on spi-nor chips.
> 
> Fix this by using proper scatter table size and intra-page buffer lengths,
so that
> the whole buffer splits into separate scatter table entries on page
boundaries.
> 
> Signed-off-by: Andrew Gabbasov <andrew_gabbasov-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/spi/spi.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 50910d8..14016dc
100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -477,7 +477,9 @@ static int spi_map_buf(struct spi_master *master,
struct
> device *dev,  {
>  	const bool vmalloced_buf = is_vmalloc_addr(buf);
>  	const int desc_len = vmalloced_buf ? PAGE_SIZE : master-
> >max_dma_len;
> -	const int sgs = DIV_ROUND_UP(len, desc_len);
> +	const int sgs = DIV_ROUND_UP(vmalloced_buf ?
> +					len + offset_in_page(buf) : len,
> +				     desc_len);
>  	struct page *vm_page;
>  	void *sg_buf;
>  	size_t min;
> @@ -488,9 +490,10 @@ static int spi_map_buf(struct spi_master *master,
> struct device *dev,
>  		return ret;
> 
>  	for (i = 0; i < sgs; i++) {
> -		min = min_t(size_t, len, desc_len);
> 
>  		if (vmalloced_buf) {
> +			min = min_t(size_t,
> +				    len, desc_len - offset_in_page(buf));
>  			vm_page = vmalloc_to_page(buf);
>  			if (!vm_page) {
>  				sg_free_table(sgt);
> @@ -499,6 +502,7 @@ static int spi_map_buf(struct spi_master *master,
struct
> device *dev,
>  			sg_set_page(&sgt->sgl[i], vm_page,
>  				    min, offset_in_page(buf));
>  		} else {
> +			min = min_t(size_t, len, desc_len);
>  			sg_buf = buf;
>  			sg_set_buf(&sgt->sgl[i], sg_buf, min);
>  		}
> --
> 2.1.0

Any opinion on this fix?

Thanks.

Best regards,
Andrew


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