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SubjectRE: [PATCH] swiotlb: add overflow checks to swiotlb_bounce
Date
> This is a follow-up on 5f89468e2f06 ("swiotlb: manipulate orig_addr when
> tlb_addr has offset") which fixed unaligned dma mappings, making sure the
> following overflows are caught:
>
> - offset of the start of the slot within the device bigger than requested
> address' offset, in other words if the base address given in
> swiotlb_tbl_map_single to create the mapping (orig_addr) was after the
> requested address for the sync (tlb_offset) in the same block:
>
> |------------------------------------------| block
> <----------------------------> mapped part of the block
> ^
> orig_addr
> ^
> invalid tlb_addr for sync
>
> - if the resulting offset was bigger than the allocation size this one
> could happen if the mapping was not until the end. e.g.
>
> |------------------------------------------| block
> <---------------------> mapped part of the block
> ^ ^
> orig_addr invalid tlb_addr
>
> Both should never happen so print a warning and bail out without trying to
> adjust the sizes/offsets: the first one could try to sync from orig_addr
> to whatever is left of the requested size, but the later really has
> nothing to sync there...
>
> Signed-off-by: Dominique Martinet <dominique.martinet@atmark-techno.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Bumyong Lee <bumyong.lee@samsung.com>

Reviewed-by: Bumyong Lee <bumyong.lee@samsung.com

> Cc: Chanho Park <chanho61.park@samsung.com>
> Cc: Christoph Hellwig <hch@lst.de>
> ---
>
> Hi Konrad,
>
> here's the follow up for the swiotlb/caamjr regression I had promissed.
> It doesn't really change anything, and I confirmed I don't hit either of
> the warnings on our board, but it's probably best to have as either could
> really happen.
>
>
> kernel/dma/swiotlb.c | 20 +++++++++++++++++---
> 1 file changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index
> e50df8d8f87e..23f8d0b168c5 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -354,13 +354,27 @@ static void swiotlb_bounce(struct device *dev,
> phys_addr_t tlb_addr, size_t size
> size_t alloc_size = mem->slots[index].alloc_size;
> unsigned long pfn = PFN_DOWN(orig_addr);
> unsigned char *vaddr = phys_to_virt(tlb_addr);
> - unsigned int tlb_offset;
> + unsigned int tlb_offset, orig_addr_offset;
>
> if (orig_addr == INVALID_PHYS_ADDR)
> return;
>
> - tlb_offset = (tlb_addr & (IO_TLB_SIZE - 1)) -
> - swiotlb_align_offset(dev, orig_addr);
> + tlb_offset = tlb_addr & (IO_TLB_SIZE - 1);
> + orig_addr_offset = swiotlb_align_offset(dev, orig_addr);
> + if (tlb_offset < orig_addr_offset) {
> + dev_WARN_ONCE(dev, 1,
> + "Access before mapping start detected. orig offset
%u,
> requested offset %u.\n",
> + orig_addr_offset, tlb_offset);
> + return;
> + }
> +
> + tlb_offset -= orig_addr_offset;
> + if (tlb_offset > alloc_size) {
> + dev_WARN_ONCE(dev, 1,
> + "Buffer overflow detected. Allocation size: %zu.
> Mapping size: %zu+%u.\n",
> + alloc_size, size, tlb_offset);
> + return;
> + }
>
> orig_addr += tlb_offset;
> alloc_size -= tlb_offset;
> --
> 2.30.2


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