On Tue, Mar 21, 2017 at 8:59 AM, Dmitry Safonov <dsafo...@virtuozzo.com> wrote: > On 03/21/2017 03:50 PM, Dmitry Safonov wrote: >> >> On 03/21/2017 03:49 PM, Thomas Gleixner wrote: >>> >>> On Tue, 21 Mar 2017, Adam Borowski wrote: >>>> >>>> On Tue, Mar 21, 2017 at 07:45:39AM +0100, Ingo Molnar wrote: >>>>> >>>>> * Andrei Vagin <ava...@gmail.com> wrote: >>>>> >>>>>> # first bad commit: [45fc8757d1d2128e342b4e7ef39adedf7752faac] x86: >>>>>> Make the GDT remapping read-only on 64-bit >>>>> >>>>> >>>>> Just wondering, does the following commit fix it: >>>>> >>>>> 5b781c7e317f x86/tls: Forcibly set the accessed bit in TLS segments >>>> >>>> >>>> It does fix i386 but not x32. >>>> >>>> By "x32" I mean CONFIG_X86_X32, by "i386" CONFIG_IA32_EMULATION, >>>> contrary to >>>> Andrei's first report. The naming of the new ABI wasn't too >>>> fortunate... >>> >>> >>> The X32 issue is unrelated to the GDT mapping. >>> >>> What happens is that the mmap rework from Dmitry switched X32 to use >>> 64bit >>> mappings, which is wrong. X32 has 64bit instructions and syscalls and >>> 32bit >>> address space. >> >> >> Hmm, in_compat_syscall() checks x32 syscall bit. > > > Which is not set during exec() for x32. So in_compat_syscall() doesn't > work there. > I've tested this patch on x32-debian port: > https://lkml.org/lkml/2017/3/21/489
Seems generally reasonable to me. It aligns x32 with existing practice for i386, I think. > > Though I'm not very happy with the resulting patch :( > Maybe one could suggest a better idea.. IMO it would be nice if execve() didn't call into any function that checked in_compat_syscall(), etc, but maybe that's a pipe dream.
