| From 9ef77ce4def3a21cc25fe647926ac917d7cf562d Mon Sep 17 00:00:00 2001 |
| From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> |
| Date: Fri, 17 Jul 2020 00:12:15 +0900 |
| Subject: [PATCH] binder: Don't use mmput() from shrinker function. |
| |
| commit f867c771f98891841c217fa8459244ed0dd28921 upstream. |
| |
| 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> |
| 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> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c |
| index bb0a732cd98a..f8953fcbcc0e 100644 |
| --- a/drivers/android/binder_alloc.c |
| +++ b/drivers/android/binder_alloc.c |
| @@ -948,7 +948,7 @@ enum lru_status binder_alloc_free_page(struct list_head *item, |
| trace_binder_unmap_user_end(alloc, index); |
| } |
| up_read(&mm->mmap_sem); |
| - mmput(mm); |
| + mmput_async(mm); |
| |
| trace_binder_unmap_kernel_start(alloc, index); |
| |
| -- |
| 2.27.0 |
| |