lkml.org 
[lkml]   [2021]   [Nov]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [REGRESSION] 5.16rc1: SA_IMMUTABLE breaks debuggers
On Wed, Nov 17, 2021 at 10:47:13AM -0800, Kyle Huey wrote:
> rr, a userspace record and replay debugger[0], is completely broken on
> 5.16rc1. I bisected this to 00b06da29cf9dc633cdba87acd3f57f4df3fd5c7.
>
> That patch makes two changes, it blocks sigaction from changing signal
> handlers once the kernel has decided to force the program to take a
> signal and it also stops notifying ptracers of the signal in the same
> circumstances. The latter behavior is just wrong. There's no reason
> that ptrace should not be able to observe and even change
> (non-SIGKILL) forced signals. It should be reverted.
>
> This behavior change is also observable in gdb. If you take a program
> that sets SIGSYS to SIG_IGN and then raises a SIGSYS via
> SECCOMP_RET_TRAP and run it under gdb on a good kernel gdb will stop
> when the SIGSYS is raised, let you inspect program state, etc. After
> the SA_IMMUTABLE change gdb won't stop until the program has already
> died of SIGSYS.

Ah, hm, this was trying to fix the case where a program trips
SECCOMP_RET_KILL (which is a "fatal SIGSYS"), and had been unobservable
before. I guess the fix was too broad...

--
Kees Cook

\
 
 \ /
  Last update: 2021-11-17 19:51    [W:0.096 / U:1.448 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site