From: Nicolin Chen <nicoleotsuka@gmail.com>
To: mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org,
rth@twiddle.net, ink@jurassic.park.msu.ru, mattst88@gmail.com,
tony.luck@intel.com, fenghua.yu@intel.com,
schnelle@linux.ibm.com, gerald.schaefer@linux.ibm.com,
hca@linux.ibm.com, gor@linux.ibm.com, borntraeger@de.ibm.com,
davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, x86@kernel.org, hpa@zytor.com,
James.Bottomley@HansenPartnership.com, deller@gmx.de
Cc: sfr@canb.auug.org.au, hch@lst.de, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org,
linux-ia64@vger.kernel.org, linux-s390@vger.kernel.org,
sparclinux@vger.kernel.org, linux-parisc@vger.kernel.org
Subject: [RESEND][PATCH 7/7] parisc: Avoid overflow at boundary_size
Date: Mon, 31 Aug 2020 13:38:11 -0700 [thread overview]
Message-ID: <20200831203811.8494-8-nicoleotsuka@gmail.com> (raw)
In-Reply-To: <20200831203811.8494-1-nicoleotsuka@gmail.com>
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>
---
drivers/parisc/ccio-dma.c | 4 ++--
drivers/parisc/sba_iommu.c | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/parisc/ccio-dma.c b/drivers/parisc/ccio-dma.c
index a5507f75b524..c667d6aba764 100644
--- a/drivers/parisc/ccio-dma.c
+++ b/drivers/parisc/ccio-dma.c
@@ -356,8 +356,8 @@ ccio_alloc_range(struct ioc *ioc, struct device *dev, size_t size)
** ggg sacrifices another 710 to the computer gods.
*/
- boundary_size = ALIGN((unsigned long long)dma_get_seg_boundary(dev) + 1,
- 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;
if (pages_needed <= 8) {
/*
diff --git a/drivers/parisc/sba_iommu.c b/drivers/parisc/sba_iommu.c
index d4314fba0269..96bc2c617cbd 100644
--- a/drivers/parisc/sba_iommu.c
+++ b/drivers/parisc/sba_iommu.c
@@ -342,8 +342,8 @@ sba_search_bitmap(struct ioc *ioc, struct device *dev,
unsigned long shift;
int ret;
- boundary_size = ALIGN((unsigned long long)dma_get_seg_boundary(dev) + 1,
- 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;
#if defined(ZX1_SUPPORT)
BUG_ON(ioc->ibase & ~IOVP_MASK);
--
2.17.1
next prev parent reply other threads:[~2020-08-31 20:39 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-31 20:38 [RESEND][PATCH 0/7] Avoid overflow at boundary_size Nicolin Chen
2020-08-31 20:38 ` [RESEND][PATCH 1/7] powerpc/iommu: " Nicolin Chen
2020-09-01 13:27 ` Michael Ellerman
2020-09-01 20:53 ` Nicolin Chen
2020-08-31 20:38 ` [RESEND][PATCH 2/7] alpha: " Nicolin Chen
2020-08-31 20:38 ` [RESEND][PATCH 3/7] ia64/sba_iommu: " Nicolin Chen
2020-08-31 20:38 ` [RESEND][PATCH 4/7] s390/pci_dma: " Nicolin Chen
2020-08-31 20:38 ` [RESEND][PATCH 5/7] sparc: " Nicolin Chen
2020-08-31 20:38 ` [RESEND][PATCH 6/7] x86/amd_gart: " Nicolin Chen
2020-08-31 20:38 ` Nicolin Chen [this message]
2020-09-01 7:36 ` [RESEND][PATCH 0/7] " Christoph Hellwig
2020-09-01 7:54 ` Nicolin Chen
2020-09-01 9:11 ` Christoph Hellwig
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