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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
(though those drivers are themselves buggy in that they should be
providing DMAable memory to the SPI framework).

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@mentor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Andrew Gabbasov 2015-06-30 10:48:37 -05:00 committed by Mark Brown
parent d770e558e2
commit 65598c13fd
1 changed files with 13 additions and 3 deletions
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16
drivers/spi/spi.c
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@ -476,21 +476,30 @@ static int spi_map_buf(struct spi_master *master, struct device *dev,
enum dma_data_direction dir)
{
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);
int desc_len;
int sgs;
struct page *vm_page;
void *sg_buf;
size_t min;
int i, ret;
if (vmalloced_buf) {
desc_len = PAGE_SIZE;
sgs = DIV_ROUND_UP(len + offset_in_page(buf), desc_len);
} else {
desc_len = master->max_dma_len;
sgs = DIV_ROUND_UP(len, desc_len);
}
ret = sg_alloc_table(sgt, sgs, GFP_KERNEL);
if (ret != 0)
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 +508,7 @@ 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);
}