[PATCH] siganl: ignore other signals when doing coredump

[Andrew Morton]

On Thu, 23 Jul 2020 14:52:23 +0800 "chunlei.wang" <Chunlei.wang at mediatek.com> wrote:

> do_coredump flow is interrupted by SIGKILL,
> causing the coredump to be truncated.
> 

Please tell us much more about why you think Linux would benefit from
this change.  Precisely what operational problems are you seeing with
the current code?


> ---
>  arch/Kconfig    | 12 ++++++++++++
>  kernel/signal.c |  8 ++++++++
>  2 files changed, 20 insertions(+)
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 8cc35dc556c7..559eac47093e 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -834,6 +834,18 @@ config OLD_SIGACTION
>  config COMPAT_OLD_SIGACTION
>  	bool
>  
> +config IGNORE_ANY_SIGNALS
> +	tristate "ignore any signals when coredump is doing"
> +	default n
> +	help
> +	  The sigkill is very special. If a process receives a sigkill, it
> will
> +	  immediately respond to the sigkill. When a process is abnormal and
> +	  collecting coredump, the do_coredump flow will be interrupted by
> +	  SIGKILL, causing the coredump to be truncated. This truncated
> coredump
> +	  is incomplete, and also gdb can't load.
> +	  Maybe we can ignore any signlas when process is collecting coredump.
> +	  This config can decide whether to ignore any signals.
> +
>  config COMPAT_32BIT_TIME
>  	bool "Provide system calls for 32-bit time_t"
>  	default !64BIT || COMPAT
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 5ca48cc5da76..ccae3c84eb6d 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -903,6 +903,14 @@ static bool prepare_signal(int sig, struct
> task_struct *p, bool force)
>  	sigset_t flush;
>  
>  	if (signal->flags & (SIGNAL_GROUP_EXIT | SIGNAL_GROUP_COREDUMP)) {
> +
> +#if defined CONFIG_IGNORE_ANY_SIGNALS
> +		if (signal->flags & SIGNAL_GROUP_COREDUMP) {
> +			pr_debug("[%d:%s] skip sig %d due to coredump is doing\n",
> +					p->pid, p->comm, sig);
> +			return false;
> +		}
> +#endif
>  		if (!(signal->flags & SIGNAL_GROUP_EXIT))
>  			return sig == SIGKILL;
>  		/*
> -- 
> 2.18.0
>