From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35202 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728047AbgIAN1x (ORCPT ); Tue, 1 Sep 2020 09:27:53 -0400 From: Michael Ellerman Subject: Re: [RESEND][PATCH 1/7] powerpc/iommu: Avoid overflow at boundary_size In-Reply-To: <20200831203811.8494-2-nicoleotsuka@gmail.com> References: <20200831203811.8494-1-nicoleotsuka@gmail.com> <20200831203811.8494-2-nicoleotsuka@gmail.com> Date: Tue, 01 Sep 2020 23:27:36 +1000 Message-ID: <87lfht1vav.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-s390-owner@vger.kernel.org List-ID: To: Nicolin Chen , 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 Nicolin Chen writes: > 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. > > Reported-by: Stephen Rothwell > Signed-off-by: Nicolin Chen > Cc: Christoph Hellwig > --- > arch/powerpc/kernel/iommu.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) Are you asking for acks, or for maintainers to merge the patches individually? > diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c > index 9704f3f76e63..c01ccbf8afdd 100644 > --- a/arch/powerpc/kernel/iommu.c > +++ b/arch/powerpc/kernel/iommu.c > @@ -236,15 +236,14 @@ static unsigned long iommu_range_alloc(struct device *dev, > } > } > > - if (dev) > - boundary_size = ALIGN(dma_get_seg_boundary(dev) + 1, > - 1 << tbl->it_page_shift); > - else > - boundary_size = ALIGN(1UL << 32, 1 << tbl->it_page_shift); > /* 4GB boundary for iseries_hv_alloc and iseries_hv_map */ > + boundary_size = dev ? dma_get_seg_boundary(dev) : U32_MAX; Is there any path that passes a NULL dev anymore? Both iseries_hv_alloc() and iseries_hv_map() were removed years ago. See: 8ee3e0d69623 ("powerpc: Remove the main legacy iSerie platform code") So maybe we should do a lead-up patch that drops the NULL dev support, which will then make this patch simpler. cheers > + /* Overflow-free shortcut for: ALIGN(b + 1, 1 << s) >> s */ > + boundary_size = (boundary_size >> tbl->it_page_shift) + 1; > > n = iommu_area_alloc(tbl->it_map, limit, start, npages, tbl->it_offset, > - boundary_size >> tbl->it_page_shift, align_mask); > + boundary_size, align_mask); > if (n == -1) { > if (likely(pass == 0)) { > /* First try the pool from the start */ > -- > 2.17.1