Messages in this thread | | | Date | Tue, 28 Mar 2017 18:27:37 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/1] get_nr_restart_syscall() should return __NR_ia32_restart_syscall if __USER32_CS |
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On 03/28, Andy Lutomirski wrote: > > On Tue, Mar 28, 2017 at 7:54 AM, Oleg Nesterov <oleg@redhat.com> wrote: > > get_nr_restart_syscall() checks TS_I386_REGS_POKED but this bit is only > > set if debugger is 32-bit. If a 64-bit debugger restores the registers > > of a 32-bit debugee outside of syscall exit path get_nr_restart_syscall() > > wrongly returns __NR_restart_syscall. > > I had sent a patch that introduced a new syscall nr, but it's not > quite safe because it could break seccomp-using programs.
Ah, indeed...
> But your > patch here is also screwy.
Yes, yes, it doesn't try to solve all possible problems, I even mentioned this in the changelog.
> How about we store the syscall arch to be restored in task_struct > along with restart_block?
Yes, perhaps we will have to finally do this. Not really nice too.
> the way there without heuristics as nasty as yours.
I agree it will be better, but I refuse to treat them as mine checks ;)
> P.S. __USER32_CS is the wrong check even if we used your approach. > user_64bit_regs() is much better.
Yes, thanks. If only I understood what cs == pv_info.extra_user_64bit_cs actually means...
OK, please ignore this patch, I'll try to make another fix.
Oleg.
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