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Tetsuo Handa f867c771f9 binder: Don't use mmput() from shrinker function. 
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 a1b2289cef ("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>
Reviewed-by: Michal Hocko <mhocko@suse.com>
Acked-by: Todd Kjos <tkjos@google.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/4ba9adb2-43f5-2de0-22de-f6075c1fab50@i-love.sakura.ne.jp
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2020-07-23 09:47:12 +02:00
..
Kconfig treewide: replace '---help---' in Kconfig files with 'help' 2020-06-14 01:57:21 +09:00
Makefile treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
binder.c binder: fix null deref of proc->context 2020-06-23 07:54:46 +02:00
binder_alloc.c binder: Don't use mmput() from shrinker function. 2020-07-23 09:47:12 +02:00
binder_alloc.h binder: return errors from buffer copy functions 2019-07-01 08:42:47 +02:00
binder_alloc_selftest.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 282 2019-06-05 17:36:37 +02:00
binder_internal.h binder: prevent UAF for binderfs devices II 2020-03-03 19:58:37 +01:00
binder_trace.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 282 2019-06-05 17:36:37 +02:00
binderfs.c binderfs: remove redundant assignment to pointer ctx 2020-04-23 16:48:11 +02:00