On Wed, 31 Mar 2021 09:44:47 +0100 Sergei Trofimovich <slyfox@xxxxxxxxxx> wrote:
> ia64 has two stacks:
> - memory stack (or stack), pointed at by by r12
> - register backing store (register stack), pointed at
> ar.bsp/ar.bspstore with complications around dirty
> register frame on CPU.
>
> In https://bugs.gentoo.org/769614 Dmitry noticed that
> PTRACE_GET_SYSCALL_INFO returns register stack instead
> memory stack.
>
> The bug comes from the fact that user_stack_pointer() and
> current_user_stack_pointer() don't return the same register:
>
> ulong user_stack_pointer(struct pt_regs *regs) { return regs->ar_bspstore; }
> #define current_user_stack_pointer() (current_pt_regs()->r12)
>
> The change gets both back in sync.
>
> I think ptrace(PTRACE_GET_SYSCALL_INFO) is the only affected user
> by this bug on ia64.
>
> The change fixes 'rt_sigreturn.gen.test' strace test where
> it was observed initially.
>
I assume a cc:stable is justified here?
The bug seems to have been there for 10+ years, so there isn't a lot of
point in looking for the Fixes: reference.
|