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Subject: Re: [PATCH 4/4] oom: fix oom_adjust_write() input sanity check.
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Paul Menage <menage@google.com>,
       David Rientjes <rientjes@google.com>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Rik van Riel <riel@redhat.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Oleg Nesterov <oleg@redhat.com>, linux-mm <linux-mm@kvack.org>
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>> @@ -1033,12 +1033,15 @@ static ssize_t oom_adjust_write(struct f
>>               count = sizeof(buffer) - 1;
>>       if (copy_from_user(buffer, buf, count))
>>               return -EFAULT;
>> +
>> +     strstrip(buffer);
>
> +1 for using strstrip()
>
> -1 for using it wrongly.  If it strips leading whitespace it will
> return a new address for the caller to use.

Will fix. thanks.

Paul, hehe your kernel/cgroup.c parsing have the same problem. Could you
please fix it too? :-)

> We could mark it __must_check() to prevent reoccurences of this error.
>
> How does this look?

I see.
I'll do and send it.

>
> --- a/fs/proc/base.c~oom-fix-oom_adjust_write-input-sanity-check-fix
> +++ a/fs/proc/base.c
> @@ -1033,8 +1033,7 @@ static ssize_t oom_adjust_write(struct f
>        if (copy_from_user(buffer, buf, count))
>                return -EFAULT;
>
> -       strstrip(buffer);
> -       oom_adjust = simple_strtol(buffer, &end, 0);
> +       oom_adjust = simple_strtol(strstrip(buffer), &end, 0);
>        if (*end)
>                return -EINVAL;
>        if ((oom_adjust < OOM_ADJUST_MIN || oom_adjust > OOM_ADJUST_MAX) &&
>
>
>>       oom_adjust = simple_strtol(buffer, &end, 0);
>
> That should've used strict_strtoul() but it's too late to fix it now.

Perhaps, it's not too late. I never seen userland program pass non number value
into this.