Re: [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack

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Subject: Re: [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Date: Sun, 20 Jun 2021 19:17:57 -0700
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>, linux-arch <linux-arch@xxxxxxxxxxxxxxx>, Jens Axboe <axboe@xxxxxxxxx>, Oleg Nesterov <oleg@xxxxxxxxxx>, Al Viro <viro@xxxxxxxxxxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Richard Henderson <rth@xxxxxxxxxxx>, Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>, Matt Turner <mattst88@xxxxxxxxx>, alpha <linux-alpha@xxxxxxxxxxxxxxx>, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>, linux-m68k <linux-m68k@xxxxxxxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxxxx>, Ley Foon Tan <ley.foon.tan@xxxxxxxxx>, Tejun Heo <tj@xxxxxxxxxx>, Kees Cook <keescook@xxxxxxxxxxxx>
In-reply-to: <393c37de-5edf-effc-3d06-d7e63f34a317@gmail.com>
References: <87sg1p30a1.fsf@disp2133> <CAHk-=wjiBXCZBxLiCG5hxpd0vMkMjiocenponWygG5SCG6DXNw@mail.gmail.com> <87pmwsytb3.fsf@disp2133> <CAHk-=wgdO5VwSUFjfF9g=DAQNYmVxzTq73NtdisYErzdZKqDGg@mail.gmail.com> <87sg1lwhvm.fsf@disp2133> <CAHk-=wgsnMTr0V-0F4FOk30Q1h7CeT8wLvR1MSnjack7EpyWtQ@mail.gmail.com> <6e47eff8-d0a4-8390-1222-e975bfbf3a65@gmail.com> <924ec53c-2fd9-2e1c-bbb1-3fda49809be4@gmail.com> <87eed4v2dc.fsf@disp2133> <5929e116-fa61-b211-342a-c706dcb834ca@gmail.com> <87fsxjorgs.fsf@disp2133> <87zgvqor7d.fsf_-_@disp2133> <CAHk-=wir2P6h+HKtswPEGDh+GKLMM6_h8aovpMcUHyQv2zJ5Og@mail.gmail.com> <87mtrpg47k.fsf@disp2133> <87pmwlek8d.fsf_-_@disp2133> <87k0mtek4n.fsf_-_@disp2133> <393c37de-5edf-effc-3d06-d7e63f34a317@gmail.com>

On Sun, Jun 20, 2021 at 7:01 PM Michael Schmitz <schmitzmic@xxxxxxxxx> wrote:


instrumenting get_reg on m68k and using a similar patch to yours to warn
when unsaved registers are accessed on the switch stack, I get a hit
from getegid and getegid32, just by running a simple ptrace on ls.

Going to wack those two moles now ...


I don't see what's going on. Those system calls don't use the register
state, afaik. What's the call chain, exactly?

           Linus

Follow-Ups:
- Re: [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack
  - From: Michael Schmitz

References:
- Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads
  - From: Eric W. Biederman
- Re: Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads
  - From: Linus Torvalds
- Re: Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads
  - From: Eric W. Biederman
- Re: Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads
  - From: Linus Torvalds
- Re: Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads
  - From: Eric W. Biederman
- Re: Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads
  - From: Linus Torvalds
- Re: Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads
  - From: Michael Schmitz
- Re: Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads
  - From: Michael Schmitz
- Re: Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads
  - From: Eric W. Biederman
- Re: Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads
  - From: Michael Schmitz
- Re: Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads
  - From: Eric W. Biederman
- [PATCH] alpha: Add extra switch_stack frames in exit, exec, and kernel threads
  - From: Eric W. Biederman
- Re: [PATCH] alpha: Add extra switch_stack frames in exit, exec, and kernel threads
  - From: Linus Torvalds
- Re: [PATCH] alpha: Add extra switch_stack frames in exit, exec, and kernel threads
  - From: Eric W. Biederman
- [PATCH 0/2] alpha/ptrace: Improved switch_stack handling
  - From: Eric W. Biederman
- [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack
  - From: Eric W. Biederman
- Re: [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack
  - From: Michael Schmitz

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