[PATCH] misc/fsck.c: Processes may kill other processes.

[PATCH] misc/fsck.c: Processes may kill other processes.

[zhanchengbin]

If run the fsck -N command, processes don't execute, just show what
would be done. However, the pid whose value is -1 is added to the
instance_list list in the execute function,if the kill_all function
is called later, kill(-1, signum) is executed, Signals are sent to
all processes except the number one process and itself. Other
processes will be killed if they use the default signal processing
function.

Signed-off-by: zhanchengbin <zhanchengbin1@huawei.com>
---
  misc/fsck.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/misc/fsck.c b/misc/fsck.c
index 4efe10ec..faf7789d 100644
--- a/misc/fsck.c
+++ b/misc/fsck.c
@@ -546,6 +546,8 @@ 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;
  		kill(inst->pid, signum);
  		n++;
  	}
-- 
2.27.0

Re: [PATCH] misc/fsck.c: Processes may kill other processes.

[Lukas Czerner]

On Sat, Oct 08, 2022 at 11:05:48AM +0800, zhanchengbin wrote:
> If run the fsck -N command, processes don't execute, just show what
> would be done. However, the pid whose value is -1 is added to the
> instance_list list in the execute function,if the kill_all function
> is called later, kill(-1, signum) is executed, Signals are sent to
> all processes except the number one process and itself. Other
> processes will be killed if they use the default signal processing
> function.
> 
> Signed-off-by: zhanchengbin <zhanchengbin1@huawei.com>
> ---
>  misc/fsck.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/misc/fsck.c b/misc/fsck.c
> index 4efe10ec..faf7789d 100644
> --- a/misc/fsck.c
> +++ b/misc/fsck.c
> @@ -546,6 +546,8 @@ 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;

That works, but I think we can afford to be a little defensive here.
Anything <= 0 is a bug and can have unexpected consequences if we
actually call the kill().

		if (inst->pid <= 0)
			continue;


Also as Darrick pointed out we need to send the patch to util-linux
(disk-utils/fsck.c) as well if you haven't already.

-Lukas


>  		kill(inst->pid, signum);
>  		n++;
>  	}
> -- 
> 2.27.0
> 

Re: [PATCH] misc/fsck.c: Processes may kill other processes.

[zhanchengbin]

On 2022/10/10 15:17, Lukas Czerner wrote:
> On Sat, Oct 08, 2022 at 11:05:48AM +0800, zhanchengbin wrote:
>> If run the fsck -N command, processes don't execute, just show what
>> would be done. However, the pid whose value is -1 is added to the
>> instance_list list in the execute function,if the kill_all function
>> is called later, kill(-1, signum) is executed, Signals are sent to
>> all processes except the number one process and itself. Other
>> processes will be killed if they use the default signal processing
>> function.
>>
>> Signed-off-by: zhanchengbin <zhanchengbin1@huawei.com>
>> ---
>>   misc/fsck.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/misc/fsck.c b/misc/fsck.c
>> index 4efe10ec..faf7789d 100644
>> --- a/misc/fsck.c
>> +++ b/misc/fsck.c
>> @@ -546,6 +546,8 @@ 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;
> 
> That works, but I think we can afford to be a little defensive here.
> Anything <= 0 is a bug and can have unexpected consequences if we
> actually call the kill().
> 
> 		if (inst->pid <= 0)
> 			continue

OK, I'll fix this and send the v2 version of the patch.

> 
> 
> Also as Darrick pointed out we need to send the patch to util-linux
> (disk-utils/fsck.c) as well if you haven't already.

I'll check and modify util-linux(disk-utils/fsck.c).

-zhanchengbin

> 
> -Lukas
> 
> 
>>   		kill(inst->pid, signum);
>>   		n++;
>>   	}
>> -- 
>> 2.27.0
>>
> 
> .
>