linux-kernel - Re: bcache: fix oops bug in cache_set

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Message-ID: <CAAsfc_p0cGqB3pj_AvfDPiYNvdk6bA77AE9cgHnf-gEa2fksRw@mail.gmail.com>
Date: Wed, 13 Nov 2024 15:40:33 +0800
From: liequan che <liequanche@...il.com>
To: Coly Li <colyli@...e.de>
Cc: Kent Overstreet <kent.overstreet@...il.com>, linux-bcache <linux-bcache@...r.kernel.org>, 
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: bcache: fix oops bug in cache_set_flush

I tested this bug on kernel versions 5.10.0-231.0.0.133 and 5.10.0-202.0.0.115。
You can get detailed information through the link below.

https://gitee.com/openeuler/kernel/issues/IB3YQZ
https://gitee.com/openeuler/kernel/pulls/13205
Best Regards！
cheleiquan

Coly Li <colyli@...e.de> 于2024年11月13日周三 15:04写道：
>
> Hi Liequan,
>
> > 2024年11月13日 14:25，liequan che <liequanche@...il.com> 写道：
> >
> > Signed-off-by: cheliequan <cheliequan@...pur.com>
> >
> >   If the bcache cache disk contains damaged btree data,
> > when the bcache cache disk partition is directly operated,
> > the system-udevd service is triggered to call the bcache-register
> > program to register the bcache device,resulting in kernel oops.
> >
>
> What is the kernel version ?
>
> Interesting that why the btree node checking code during registration doesn’t cache the meta data error.
>
>
>
> > crash> bt
> > PID: 7773     TASK: ffff49cc44d69340  CPU: 57   COMMAND: "kworker/57:2"
> > #0 [ffff800046373800] machine_kexec at ffffbe5039eb54a8
> > #1 [ffff8000463739b0] __crash_kexec at ffffbe503a052824
> > #2 [ffff8000463739e0] crash_kexec at ffffbe503a0529cc
> > #3 [ffff800046373a60] die at ffffbe5039e9445c
> > #4 [ffff800046373ac0] die_kernel_fault at ffffbe5039ec698c
> > #5 [ffff800046373af0] __do_kernel_fault at ffffbe5039ec6a38
> > #6 [ffff800046373b20] do_page_fault at ffffbe503ac76ba4
> > #7 [ffff800046373b70] do_translation_fault at ffffbe503ac76ebc
> > #8 [ffff800046373b90] do_mem_abort at ffffbe5039ec68ac
> > #9 [ffff800046373bc0] el1_abort at ffffbe503ac669bc
> > #10 [ffff800046373bf0] el1_sync_handler at ffffbe503ac671d4
> > #11 [ffff800046373d30] el1_sync at ffffbe5039e82230
> > #12 [ffff800046373d50] cache_set_flush at ffffbe50121fa4c4 [bcache]
> > #13 [ffff800046373da0] process_one_work at ffffbe5039f5af68
> > #14 [ffff800046373e00] worker_thread at ffffbe5039f5b3c4
> > #15 [ffff800046373e50] kthread at ffffbe5039f634b8
> > crash> dis cache_set_flush+0x94
> > 0xffffbe50121fa4c8 <cache_set_flush+148>:       str     x23, [x20, #512]
> >
> > ---
> > drivers/md/bcache/super.c | 16 ++++++++++------
> > 1 file changed, 10 insertions(+), 6 deletions(-)
> > diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> > index fd97730479d8..8a41dfcf9fb6 100644
> > --- a/drivers/md/bcache/super.c
> > +++ b/drivers/md/bcache/super.c
> > @@ -1741,8 +1741,10 @@ static void cache_set_flush(struct closure *cl)
> >       if (!IS_ERR_OR_NULL(c->gc_thread))
> >               kthread_stop(c->gc_thread);
> >
> > -       if (!IS_ERR(c->root))
> > -               list_add(&c->root->list, &c->btree_cache);
> > +       if (!IS_ERR_OR_NULL(c->root)) {
> > +               if (!list_empty(&c->root->list))
> > +                       list_add(&c->root->list, &c->btree_cache);
> > +       }
> >
> >       /*
> >        * Avoid flushing cached nodes if cache set is retiring
> > @@ -1750,10 +1752,12 @@ static void cache_set_flush(struct closure *cl)
> >        */
> >       if (!test_bit(CACHE_SET_IO_DISABLE, &c->flags))
> >               list_for_each_entry(b, &c->btree_cache, list) {
> > -                       mutex_lock(&b->write_lock);
> > -                       if (btree_node_dirty(b))
> > -                               __bch_btree_node_write(b, NULL);
> > -                       mutex_unlock(&b->write_lock);
> > +                       if (!IS_ERR_OR_NULL(b)) {
>
> The above check is not safe.
>
>
>
> > +                               mutex_lock(&b->write_lock);
> > +                               if (btree_node_dirty(b))
> > +                                       __bch_btree_node_write(b, NULL);
> > +                               mutex_unlock(&b->write_lock);
> > +                       }
> >               }
> >
> >       if (ca->alloc_thread)
> > --
> > 2.33.0
>
>
> Thanks.
>
> Coly Li