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[37.188.169.187]) by smtp.gmail.com with ESMTPSA id b17sm9755636wrp.32.2020.07.16.08.17.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Jul 2020 08:17:57 -0700 (PDT) Date: Thu, 16 Jul 2020 17:17:56 +0200 From: Michal Hocko To: Tetsuo Handa Cc: Greg Kroah-Hartman , Arve Hjonnevag , Todd Kjos , Martijn Coenen , Joel Fernandes , Christian Brauner , syzbot , acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, linux-kernel@vger.kernel.org, mark.rutland@arm.com, mingo@redhat.com, namhyung@kernel.org, peterz@infradead.org, syzkaller-bugs@googlegroups.com, "open list:ANDROID DRIVERS" , linux-mm Subject: Re: [PATCH v2] binder: Don't use mmput() from shrinker function. Message-ID: <20200716151756.GO31089@dhcp22.suse.cz> References: <0000000000001fbbb605aa805c9b@google.com> <5ce3ee90-333e-638d-ac8c-cd6d7ab7aa3b@I-love.SAKURA.ne.jp> <20200716083506.GA20915@dhcp22.suse.cz> <36db7016-98d6-2c6b-110b-b2481fd480ac@i-love.sakura.ne.jp> <20200716135445.GN31089@dhcp22.suse.cz> <4ba9adb2-43f5-2de0-22de-f6075c1fab50@i-love.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4ba9adb2-43f5-2de0-22de-f6075c1fab50@i-love.sakura.ne.jp> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 17-07-20 00:12:15, Tetsuo Handa wrote: > syzbot is reporting that mmput() from shrinker function has a risk of > deadlock [1], for delayed_uprobe_add() from update_ref_ctr() calls > kzalloc(GFP_KERNEL) with delayed_uprobe_lock held, and > uprobe_clear_state() from __mmput() also holds delayed_uprobe_lock. > > Commit a1b2289cef92ef0e ("android: binder: drop lru lock in isolate > callback") replaced mmput() with mmput_async() in order to avoid sleeping > with spinlock held. But this patch replaces mmput() with mmput_async() in > order not to start __mmput() from shrinker context. > > [1] https://syzkaller.appspot.com/bug?id=bc9e7303f537c41b2b0cc2dfcea3fc42964c2d45 > > Reported-by: syzbot > Reported-by: syzbot > Signed-off-by: Tetsuo Handa Reviewed-by: Michal Hocko Thanks! > --- > drivers/android/binder_alloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c > index 42c672f1584e..cbe6aa77d50d 100644 > --- a/drivers/android/binder_alloc.c > +++ b/drivers/android/binder_alloc.c > @@ -947,7 +947,7 @@ enum lru_status binder_alloc_free_page(struct list_head *item, > trace_binder_unmap_user_end(alloc, index); > } > mmap_read_unlock(mm); > - mmput(mm); > + mmput_async(mm); > > trace_binder_unmap_kernel_start(alloc, index); > > -- > 2.18.4 -- Michal Hocko SUSE Labs