linux-ext4 - Re: [bug report] misc/fsck.c: Processes may kill other processes.

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Date:   Fri, 30 Sep 2022 09:20:42 +0200
From:   Lukas Czerner <lczerner@...hat.com>
To:     zhanchengbin <zhanchengbin1@...wei.com>
Cc:     Theodore Ts'o <tytso@....edu>, linux-ext4@...r.kernel.org,
        liuzhiqiang26@...wei.com, linfeilong <linfeilong@...wei.com>
Subject: Re: [bug report] misc/fsck.c: Processes may kill other processes.

On Fri, Sep 30, 2022 at 09:42:52AM +0800, zhanchengbin wrote:
> 
> 
> On 2022/9/29 19:28, Lukas Czerner wrote:
> > Hi,
> > 
> > indeed we'd like to avoid killing the instance that was not ran because
> > of noexecute. Can you try the following patch?
> > 
> > Thanks!
> > -Lukas
> 
> Yes, you're right, I think we can fix it in this way.
> 
> diff --git a/misc/fsck.c b/misc/fsck.c
> index 1f6ec7d9..91edbf17 100644
> --- a/misc/fsck.c
> +++ b/misc/fsck.c
> @@ -547,6 +547,8 @@ static int kill_all(int signum)
>         for (inst = instance_list; inst; inst = inst->next) {
>                 if (inst->flags & FLAG_DONE)
>                         continue;
> +               if (inst->pid == -1)
> +                       continue;

Yeah, that works as well although I find the "if (noexecute)" condition
more obvious. We can do both. Also rather than checking for -1 we can
check for <= 0 since anything other than real pid at this point is a bug.

Feel free to send a proper patch.

Thanks!
-Lukas

>                 kill(inst->pid, signum);
>                 n++;
>         }
> > 
> > 
> > diff --git a/misc/fsck.c b/misc/fsck.c
> > index 1f6ec7d9..8fae7730 100644
> > --- a/misc/fsck.c
> > +++ b/misc/fsck.c
> > @@ -497,9 +497,10 @@ static int execute(const char *type, const char *device, const char *mntpt,
> >   	}
> >   	/* Fork and execute the correct program. */
> > -	if (noexecute)
> > +	if (noexecute) {
> >   		pid = -1;
> > -	else if ((pid = fork()) < 0) {
> > +		inst->flags |= FLAG_DONE;
> > +	} else if ((pid = fork()) < 0) {
> >   		perror("fork");
> >   		free(inst);
> >   		return errno;
> > @@ -544,6 +545,9 @@ static int kill_all(int signum)
> >   	struct fsck_instance *inst;
> >   	int	n = 0;
> > +	if (noexecute)
> > +		return 0;
> > +
> >   	for (inst = instance_list; inst; inst = inst->next) {
> >   		if (inst->flags & FLAG_DONE)
> >   			continue;
> regards,
> Zhan Chengbin
>