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:   Wed, 9 Sep 2020 22:52:09 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Chris Down <chris@...isdown.name>
Cc:     Vlastimil Babka <vbabka@...e.cz>, 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 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.

        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));
}