Date: Mon, 10 Jun 2019 09:35:17 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: Doug Moore <dougm@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r348843 - head/sys/vm Message-ID: <c54a0e35-d5c6-0711-d2bb-01e3dca802c3@FreeBSD.org> In-Reply-To: <201906100307.x5A37BFt099669@repo.freebsd.org> References: <201906100307.x5A37BFt099669@repo.freebsd.org>
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On 10/06/2019 06:07, Doug Moore wrote: > Author: dougm > Date: Mon Jun 10 03:07:10 2019 > New Revision: 348843 > URL: https://svnweb.freebsd.org/changeset/base/348843 > > Log: > There are times when a len==0 parameter to mmap is okay. But on a > 32-bit machine, a len parameter just a few bytes short of 4G, rounded > up to a page boundary and hitting zero then, is not okay. Return > failure in that case. > > Reported by: pho > Reviewed by: alc, kib (mentor) > Tested by: pho > Differential Revision: https://reviews.freebsd.org/D20580 > > Modified: > head/sys/vm/vm_mmap.c > > Modified: head/sys/vm/vm_mmap.c > ============================================================================== > --- head/sys/vm/vm_mmap.c Sun Jun 9 22:55:21 2019 (r348842) > +++ head/sys/vm/vm_mmap.c Mon Jun 10 03:07:10 2019 (r348843) > @@ -257,7 +257,10 @@ kern_mmap(struct thread *td, uintptr_t addr0, size_t s > > /* Adjust size for rounding (on both ends). */ > size += pageoff; /* low end... */ > - size = (vm_size_t) round_page(size); /* hi end */ > + /* Check for rounding up to zero. */ > + if (round_page(size) < size) Is this guaranteed to work with all compilers? I think that some smart compilers may think that this condition is impossible. Are we finally using -fwrapv or something like it for kernel builds? > + return (EINVAL); > + size = round_page(size); /* hi end */ > > /* Ensure alignment is at least a page and fits in a pointer. */ > align = flags & MAP_ALIGNMENT_MASK; > -- Andriy Gapon
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