Re: [tip:x86/vdso] x86/vdso32/syscall.S: Do not load __USER32_DS to %ss
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- Subject: Re: [tip:x86/vdso] x86/vdso32/syscall.S: Do not load __USER32_DS to %ss
- From: Borislav Petkov <bp@xxxxxxxxx>
- Date: Thu, 23 Apr 2015 19:14:40 +0200
- Cc: Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx>, Denys Vlasenko <dvlasenk@xxxxxxxxxx>, Brian Gerst <brgerst@xxxxxxxxx>, Steven Rostedt <rostedt@xxxxxxxxxxx>, Oleg Nesterov <oleg@xxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxx>, Will Drewry <wad@xxxxxxxxxxxx>, Frédéric Weisbecker <fweisbec@xxxxxxxxx>, Alexei Starovoitov <ast@xxxxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Kees Cook <keescook@xxxxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, "linux-tip-commits@xxxxxxxxxxxxxxx" <linux-tip-commits@xxxxxxxxxxxxxxx>
- In-reply-to: <CALCETrUHUJeVWC+qAwvrDF1dvPMY7jZcNNVh2gM77pw3db9JVg@mail.gmail.com>
- User-agent: Mutt/1.5.23 (2014-03-12)
On Thu, Apr 23, 2015 at 09:50:17AM -0700, Andy Lutomirski wrote:
> On Thu, Apr 23, 2015 at 9:41 AM, Denys Vlasenko
> <vda.linux@xxxxxxxxxxxxxx> wrote:
> > An alternative fix would be, if we decided to schedule
> > in an interrupt, check %ss for zero and reload it
> > with __KERNEL_DS before schedule.
>
> For anyone who has the right hardware (not me!), a possible reproducer is here:
>
> https://git.kernel.org/cgit/linux/kernel/git/luto/misc-tests.git/
>
> make && taskset -c 0 ./sysret_ss_attrs_32
[ 195.438441] traps: sysret_ss_attrs[1745] trap stack segment ip:f77dab87 sp:ffdf0b70 error:0
[ 196.831952] traps: sysret_ss_attrs[1748] trap stack segment ip:f7786b87 sp:fffc0810 error:0
Ran it twice.
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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