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Subject: [media] v4l: vb2-dma-contig: fail if user ptr buffer is not correctly 
aligned
Author:  Marek Szyprowski <[email protected]>
Date:    Tue Jun 12 10:18:16 2012 -0300

The DMA transfer must be aligned to a specific value. If userptr is not aligned
to DMA requirements then unexpected corruptions of the memory may occur before
or after a buffer.  To prevent such situations, all unligned userptr buffers
are rejected at VIDIOC_QBUF.

Signed-off-by: Marek Szyprowski <[email protected]>
Acked-by: Hans Verkuil <[email protected]>
Signed-off-by: Mauro Carvalho Chehab <[email protected]>

 drivers/media/v4l2-core/videobuf2-dma-contig.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

---

http://git.linuxtv.org/media_tree.git?a=commitdiff;h=d81e870d5afa1b0a95ea94c4052d3c7e973fae8c

diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c 
b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index b35f38e..27de1bb 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -491,6 +491,18 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned 
long vaddr,
        struct vm_area_struct *vma;
        struct sg_table *sgt;
        unsigned long contig_size;
+       unsigned long dma_align = dma_get_cache_alignment();
+
+       /* Only cache aligned DMA transfers are reliable */
+       if (!IS_ALIGNED(vaddr | size, dma_align)) {
+               pr_debug("user data must be aligned to %lu bytes\n", dma_align);
+               return ERR_PTR(-EINVAL);
+       }
+
+       if (!size) {
+               pr_debug("size is zero\n");
+               return ERR_PTR(-EINVAL);
+       }
 
        buf = kzalloc(sizeof *buf, GFP_KERNEL);
        if (!buf)

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