Re: [PATCH 2/2] exec: Make do_coredump more robust and safer whenusing pipes in core_pattern: wait for core collectors

[Oleg Nesterov]

On 06/26, Neil Horman wrote:
>
> - 		if (call_usermodehelper_pipe(corename+1, helper_argv, NULL,
> -				&file)) {
> + 		if (call_usermodehelper_pipe(helper_argv[0], helper_argv, NULL,
> +				&file, &pid) < 0) {

...


> +	if (ispipe && core_pipe_limit)
> +		sys_wait4(pid, NULL, 0, NULL);

How this can work? sys_wait4() can only wait for our childs, but the parent
of the dumping thread is khelper.


If we change kmod.c, then I think we need UMH_WAIT_CUSTOM_COMPLETION.


But perhaps do_coredump() can just sleep on file->...->i_pipe->wait waiting
for pipe_inode_info->readers == 0 ?

Oleg.

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