Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Nicolin Chen <> | Subject | [RFT][PATCH 3/7] ia64/sba_iommu: Avoid overflow at boundary_size | Date | Thu, 20 Aug 2020 16:20:18 -0700 |
| |
The boundary_size might be as large as ULONG_MAX, which means that a device has no specific boundary limit. So either "+ 1" or passing it to ALIGN() would potentially overflow.
According to kernel defines: #define ALIGN_MASK(x, mask) (((x) + (mask)) & ~(mask)) #define ALIGN(x, a) ALIGN_MASK(x, (typeof(x))(a) - 1)
We can simplify the logic here: ALIGN(boundary + 1, 1 << shift) >> shift = ALIGN_MASK(b + 1, (1 << s) - 1) >> s = {[b + 1 + (1 << s) - 1] & ~[(1 << s) - 1]} >> s = [b + 1 + (1 << s) - 1] >> s = [b + (1 << s)] >> s = (b >> s) + 1
So fixing a potential overflow with the safer shortcut.
Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com> Cc: Christoph Hellwig <hch@lst.de> --- arch/ia64/hp/common/sba_iommu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/ia64/hp/common/sba_iommu.c b/arch/ia64/hp/common/sba_iommu.c index 656a4888c300..945954903bb0 100644 --- a/arch/ia64/hp/common/sba_iommu.c +++ b/arch/ia64/hp/common/sba_iommu.c @@ -485,8 +485,8 @@ sba_search_bitmap(struct ioc *ioc, struct device *dev, ASSERT(((unsigned long) ioc->res_hint & (sizeof(unsigned long) - 1UL)) == 0); ASSERT(res_ptr < res_end); - boundary_size = (unsigned long long)dma_get_seg_boundary(dev) + 1; - boundary_size = ALIGN(boundary_size, 1ULL << iovp_shift) >> iovp_shift; + /* Overflow-free shortcut for: ALIGN(b + 1, 1 << s) >> s */ + boundary_size = (dma_get_seg_boundary(dev) >> iovp_shift) + 1; BUG_ON(ioc->ibase & ~iovp_mask); shift = ioc->ibase >> iovp_shift; -- 2.17.1
| ![\](/images/icornerr.gif) |