Re: Compat 32-bit syscall entry from 64-bit task!? [was: Re: [RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF]

[Andi Kleen]

> Our ptrace jailer is checking cs to figure out if a task is a compat task
> or not, if the kernel can change that behind our back it means our jailer

Every user program change it behind your back.

Your ptrace jailer isn't.

> I think this behaviour is so unexpected that it can only cause security
> problems in the long run. Is anyone counting on this? Where is this
> behaviour documented?

Look up far jumps in any x86 manual.

-Andi
-- 
ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
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