linux-kernel - Re: [PATCH v2] mm/vmscan: fix infinite loop in drop_slab

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 10 Sep 2020 00:13:48 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Matthew Wilcox <willy@...radead.org>,
        Chris Down <chris@...isdown.name>
Cc:     zangchunxin@...edance.com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: Re: [PATCH v2] mm/vmscan: fix infinite loop in drop_slab_node

On 9/9/20 11:52 PM, Matthew Wilcox wrote:
> On Wed, Sep 09, 2020 at 10:47:24PM +0100, Chris Down wrote:
>> Vlastimil Babka writes:
>> > - Exit also on other signals such as SIGABRT, SIGTERM? If I write to drop_caches
>> > and think it's too long, I would prefer to kill it by ctrl-c and not just kill
>> 
>> Oh dear, fatal_signal_pending() doesn't consider cases with no more
>> userspace instructions due to SIG_DFL on TERM/INT etc, that seems misleading
>> :-( I had (naively) believed it internally checks the same set as
>> TASK_KILLABLE.
>> 
>> Chuxin, Muchun, can you please make it work using TASK_KILLABLE in a similar
>> way to how schedule_timeout_killable and friends do it instead, so that
>> other signals will be caught?
> 
> You're mistaken.

Ah actually it was me who thought fatal_signal_pending() was only for SIGKILL,
OOM and whatnot. Sorry for the noise.

>         if (sig_fatal(p, sig) &&
>             !(signal->flags & SIGNAL_GROUP_EXIT) &&
>             !sigismember(&t->real_blocked, sig) &&
>             (sig == SIGKILL || !p->ptrace)) {
> ...
>                                 sigaddset(&t->pending.signal, SIGKILL);
> 
> static inline int __fatal_signal_pending(struct task_struct *p)
> {
>         return unlikely(sigismember(&p->pending.signal, SIGKILL));
> }
>