From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Arve Hjonnevag <arve@android.com>, Todd Kjos <tkjos@android.com>,
Martijn Coenen <maco@android.com>,
Joel Fernandes <joel@joelfernandes.org>,
Christian Brauner <christian@brauner.io>
Cc: Michal Hocko <mhocko@kernel.org>,
syzbot <syzbot+e5344baa319c9a96edec@syzkaller.appspotmail.com>,
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" <devel@driverdev.osuosl.org>,
linux-mm <linux-mm@kvack.org>
Subject: [PATCH v2] binder: Don't use mmput() from shrinker function.
Date: Fri, 17 Jul 2020 00:12:15 +0900 [thread overview]
Message-ID: <4ba9adb2-43f5-2de0-22de-f6075c1fab50@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20200716135445.GN31089@dhcp22.suse.cz>
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 <syzbot+1068f09c44d151250c33@syzkaller.appspotmail.com>
Reported-by: syzbot <syzbot+e5344baa319c9a96edec@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
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
next prev parent reply other threads:[~2020-07-16 15:12 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-15 19:59 possible deadlock in uprobe_clear_state (2) syzbot
2020-07-15 23:36 ` [PATCH] binder: Don't use mmput() from shrinker function Tetsuo Handa
2020-07-16 8:35 ` Michal Hocko
2020-07-16 13:41 ` Tetsuo Handa
2020-07-16 13:54 ` Michal Hocko
2020-07-16 15:12 ` Tetsuo Handa [this message]
2020-07-16 15:17 ` [PATCH v2] " Michal Hocko
2020-07-16 16:29 ` Christian Brauner
2020-07-16 22:27 ` Tetsuo Handa
2020-07-16 23:53 ` Todd Kjos
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