| Date | Mon, 13 Sep 2021 09:20:26 -0700 | From | Kees Cook <> | Subject | Re: [PATCH 00/10] raise minimum GCC version to 5.1 |
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On Mon, Sep 13, 2021 at 11:49:48AM +0200, Pavel Machek wrote: > Hi! > > > commit fad7cd3310db ("nbd: add the check to prevent overflow in > > __nbd_ioctl()") > > > > raised an issue from the fallback helpers added in > > > > commit f0907827a8a9 ("compiler.h: enable builtin overflow checkers and add fallback code") > > > > Specifically, the helpers for checking whether the results of a > > multiplication overflowed (__unsigned_mul_overflow, > > __signed_add_overflow) use the division operator when > > !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW. This is problematic for 64b > > operands on 32b hosts. > > Please don't. gcc 4.9.2 is still in use here. > > Plus, someone will want to prevent overflow in -stable, too, and you > can't really raise gcc version there.
These changes won't go to prior stable kernels.
-- Kees Cook
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