From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicolin Chen Subject: [RESEND][PATCH 4/7] s390/pci_dma: Avoid overflow at boundary_size Date: Mon, 31 Aug 2020 13:38:08 -0700 Message-ID: <20200831203811.8494-5-nicoleotsuka@gmail.com> References: <20200831203811.8494-1-nicoleotsuka@gmail.com> Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=UkH8Mq/WpiesfkXrapLTRLCROpdsRyoJty+98OOSpss=; b=QBwNrPdfcSAA97dtBnIWUfFN68G3dlx1D0NnviFoEsXwwJ685l3hFpoUYeYtJQzsk/ fa7q/UtZxp6YwHBe+lUXHOQ1+GfSZzVh/DlB4nJjGv8Y+GG4bROeovNbk90Dcxd5OiaP gYkpuhwWCgw69+Fd2vWpUnQw4H4CpId8WgPawlAj3OSXL312ysfq8SYTiTBN4xm5ThPO F5+hNzC4yo3iGIb2RECwzNn7zXfvrk0NhPLH5HEpZ91StyGiVU6TKHdKBob3F9RMPnA2 XmuYHqTMy4gsXlEfIEJipnHZkQI0n3KRv58zBJxo9DDi8lOQS6j3A/NxhJQ1wSezy3yl U1oQ== In-Reply-To: <20200831203811.8494-1-nicoleotsuka@gmail.com> Sender: linux-parisc-owner@vger.kernel.org List-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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 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 Cc: Christoph Hellwig --- arch/s390/pci/pci_dma.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c index 64b1399a73f0..ecb067acc6d5 100644 --- a/arch/s390/pci/pci_dma.c +++ b/arch/s390/pci/pci_dma.c @@ -263,8 +263,8 @@ static unsigned long __dma_alloc_iommu(struct device *dev, struct zpci_dev *zdev = to_zpci(to_pci_dev(dev)); unsigned long boundary_size; - boundary_size = ALIGN(dma_get_seg_boundary(dev) + 1, - PAGE_SIZE) >> PAGE_SHIFT; + /* Overflow-free shortcut for: ALIGN(b + 1, 1 << s) >> s */ + boundary_size = (dma_get_seg_boundary(dev) >> PAGE_SHIFT) + 1; return iommu_area_alloc(zdev->iommu_bitmap, zdev->iommu_pages, start, size, zdev->start_dma >> PAGE_SHIFT, boundary_size, 0); -- 2.17.1