Re: [PATCH v3 1/4] panic: Add a platform panic notifier list

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Medium] crash: kexec_trylock() held across panic_notify_platform()
  breaks kdump
--

commit 27b42ef2d74e73a1aad7b08a71b2e46383b32891
Author: Zack Rusin <zack.rusin@broadcom.com>

panic: Add a platform panic notifier list

This commit adds a platform panic notifier list (panic_notifiers_platform_list)
that runs early in vpanic() and in __crash_kexec(), along with a kernel
parameter to disable it.

Link: https://lore.kernel.org/r/ateYxCu63pRY9EGq@pathway.suse.cz

> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index d0bd2d0cf8990..10b4384294c2b 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
[ ... ]
> @@ -139,6 +140,8 @@ void __noclone __crash_kexec(struct pt_regs *regs)
>  			struct pt_regs fixed_regs;
>  
>  			crash_setup_regs(&fixed_regs, regs);
> +			/* For crash paths that bypass panic() */
> +			panic_notify_platform();
>  			crash_save_vmcoreinfo();
>  			machine_crash_shutdown(&fixed_regs);
>  			crash_cma_clear_pending_dma();

[Severity: Medium]
Can calling panic_notify_platform() while kexec_trylock() is held prevent
kdump from running if a platform notifier callback panics?

panic_notify_platform() sets done = true before invoking the notifier
chain so that a callback that panics will not re-run the list when it
enters vpanic().  However, when __crash_kexec() is entered directly on a
crash path that bypasses panic() (such as oops_end() -> crash_kexec()),
__kexec_lock is already held:

  crash_kexec()
    __crash_kexec(regs)
      kexec_trylock()
      panic_notify_platform()
        <callback panics>
          vpanic()
            __crash_kexec(NULL)
              kexec_trylock()  <-- fails, skips kdump

Because vpanic() never returns to the outer __crash_kexec() frame,
machine_kexec() is never reached and the crash dump is lost.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1794201807.git.zack.rusin@broadcom.com?part=1