On 10/06/2019 09:42, Doug Moore wrote: > -fwrapv concerns signed arithmetic. This calculation is with unsigned > arithmetic, and the possibility of wrapping around to 0 is part of the > language.
Oh, sorry for the noise! > On 6/10/19 1:35 AM, Andriy Gapon wrote: >> 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 _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
