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Subject[PATCH] swiotlb: add overflow checks to swiotlb_bounce
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
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 <>
Cc: Konrad Rzeszutek Wilk <>
Cc: Bumyong Lee <>
Cc: Chanho Park <>
Cc: Christoph Hellwig <>

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)

- 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;

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