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authorTetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>2021-08-04 19:26:56 +0900
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-08-15 12:59:55 +0200
commitd6ef8bb00aa65eceb413fc165a55086459863e38 (patch)
treec72b29ad6ab6b0efe99da26188ae01ee54c1207a /include
parent914054dc07500ed7836562001f1b9cb0e96c7d5e (diff)
Bluetooth: defer cleanup of resources in hci_unregister_dev()
[ Upstream commit e04480920d1eec9c061841399aa6f35b6f987d8b ] syzbot is hitting might_sleep() warning at hci_sock_dev_event() due to calling lock_sock() with rw spinlock held [1]. It seems that history of this locking problem is a trial and error. Commit b40df5743ee8 ("[PATCH] bluetooth: fix socket locking in hci_sock_dev_event()") in 2.6.21-rc4 changed bh_lock_sock() to lock_sock() as an attempt to fix lockdep warning. Then, commit 4ce61d1c7a8e ("[BLUETOOTH]: Fix locking in hci_sock_dev_event().") in 2.6.22-rc2 changed lock_sock() to local_bh_disable() + bh_lock_sock_nested() as an attempt to fix the sleep in atomic context warning. Then, commit 4b5dd696f81b ("Bluetooth: Remove local_bh_disable() from hci_sock.c") in 3.3-rc1 removed local_bh_disable(). Then, commit e305509e678b ("Bluetooth: use correct lock to prevent UAF of hdev object") in 5.13-rc5 again changed bh_lock_sock_nested() to lock_sock() as an attempt to fix CVE-2021-3573. This difficulty comes from current implementation that hci_sock_dev_event(HCI_DEV_UNREG) is responsible for dropping all references from sockets because hci_unregister_dev() immediately reclaims resources as soon as returning from hci_sock_dev_event(HCI_DEV_UNREG). But the history suggests that hci_sock_dev_event(HCI_DEV_UNREG) was not doing what it should do. Therefore, instead of trying to detach sockets from device, let's accept not detaching sockets from device at hci_sock_dev_event(HCI_DEV_UNREG), by moving actual cleanup of resources from hci_unregister_dev() to hci_cleanup_dev() which is called by bt_host_release() when all references to this unregistered device (which is a kobject) are gone. Since hci_sock_dev_event(HCI_DEV_UNREG) no longer resets hci_pi(sk)->hdev, we need to check whether this device was unregistered and return an error based on HCI_UNREGISTER flag. There might be subtle behavioral difference in "monitor the hdev" functionality; please report if you found something went wrong due to this patch. Link: https://syzkaller.appspot.com/bug?extid=a5df189917e79d5e59c9 [1] Reported-by: syzbot <syzbot+a5df189917e79d5e59c9@syzkaller.appspotmail.com> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Fixes: e305509e678b ("Bluetooth: use correct lock to prevent UAF of hdev object") Acked-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'include')
-rw-r--r--include/net/bluetooth/hci_core.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index f042188c8099..e1e181059324 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -1013,6 +1013,7 @@ struct hci_dev *hci_alloc_dev(void);
void hci_free_dev(struct hci_dev *hdev);
int hci_register_dev(struct hci_dev *hdev);
void hci_unregister_dev(struct hci_dev *hdev);
+void hci_cleanup_dev(struct hci_dev *hdev);
int hci_suspend_dev(struct hci_dev *hdev);
int hci_resume_dev(struct hci_dev *hdev);
int hci_reset_dev(struct hci_dev *hdev);