From: Oleg Nesterov <oleg@redhat.com>
To: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Sherry Yang <sherryy@android.com>, Michal Hocko <mhocko@suse.com>,
srikar@linux.vnet.ibm.com, songliubraving@fb.com,
peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
alexander.shishkin@linux.intel.com, jolsa@redhat.com,
namhyung@kernel.org, linux-kernel@vger.kernel.org,
aneesh.kumar@linux.ibm.com,
syzbot+1068f09c44d151250c33@syzkaller.appspotmail.com
Subject: Re: [PATCH] Uprobes: Fix deadlock between delayed_uprobe_lock and fs_reclaim
Date: Tue, 26 Feb 2019 17:20:50 +0100 [thread overview]
Message-ID: <20190226162049.GB21443@redhat.com> (raw)
In-Reply-To: <611d2ba9-c14b-4580-a7ec-8bcf0013cd6b@linux.ibm.com>
On 02/26, Ravi Bangoria wrote:
>
> On 2/8/19 2:03 PM, Ravi Bangoria wrote:
> >
> >
> > On 2/6/19 7:06 PM, Oleg Nesterov wrote:
> >> Ravi, I am on vacation till the end of this week, can't read your patch
> >> carefully.
> >>
> >> I am not sure I fully understand the problem, but shouldn't we change
> >> binder_alloc_free_page() to use mmput_async() ? Like it does if trylock
> >> fails.
> >
> > I don't understand binderfs code much so I'll let Sherry comment on this.
>
> Sherry, Can you please comment on this.
Yes, please. I don't even know what android/binder does, but I think we need
the trivial patch below.
If nothing else, any reason why err_down_write_mmap_sem_failed needs _async
should equally apply to the case when down_write_trylock() succeeds, no?
And. This lockdep report basically means that (without this change) kmalloc
is not safe under any lock which can be taken in __mmput() path, I don't think
we should blame or change uprobes.c.
Oleg.
--- x/drivers/android/binder_alloc.c
+++ x/drivers/android/binder_alloc.c
@@ -981,7 +981,7 @@ enum lru_status binder_alloc_free_page(s
trace_binder_unmap_user_end(alloc, index);
up_write(&mm->mmap_sem);
- mmput(mm);
+ mmput_async(mm);
}
trace_binder_unmap_kernel_start(alloc, index);
prev parent reply other threads:[~2019-02-26 16:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-04 4:06 [PATCH] Uprobes: Fix deadlock between delayed_uprobe_lock and fs_reclaim Ravi Bangoria
2019-02-06 13:36 ` Oleg Nesterov
2019-02-08 8:33 ` Ravi Bangoria
2019-02-26 3:53 ` Ravi Bangoria
2019-02-26 16:20 ` Oleg Nesterov [this message]
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