Bluetooth: call lock_sock() outside of spinlock section

Commit Message

Tetsuo Handa June 27, 2021, 1:11 p.m. UTC

syzbot is hitting might_sleep() warning at hci_sock_dev_event() due to
calling lock_sock() with rw spinlock held [1]. Defer calling lock_sock()
via sock_hold().

Link: https://syzkaller.appspot.com/bug?extid=a5df189917e79d5e59c9 [1]
Reported-by: syzbot <[e-mail]>
Signed-off-by: Tetsuo Handa <[e-mail]>
Tested-by: syzbot <[e-mail]>
Fixes: e305509e678b3a4a ("Bluetooth: use correct lock to prevent UAF of hdev object")
---
 net/bluetooth/hci_sock.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

Comments

[e-mail] June 27, 2021, 2:05 p.m. UTC | #1

This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=507659

---Test result---

Test Summary:
CheckPatch                    PASS      0.88 seconds
GitLint                       FAIL      0.12 seconds
BuildKernel                   PASS      542.37 seconds
TestRunner: Setup             PASS      358.20 seconds
TestRunner: l2cap-tester      PASS      2.78 seconds
TestRunner: bnep-tester       PASS      1.91 seconds
TestRunner: mgmt-tester       FAIL      33.12 seconds
TestRunner: rfcomm-tester     PASS      2.30 seconds
TestRunner: sco-tester        PASS      2.07 seconds
TestRunner: smp-tester        PASS      2.25 seconds
TestRunner: userchan-tester   PASS      2.08 seconds

Details
##############################
Test: CheckPatch - PASS - 0.88 seconds
Run checkpatch.pl script with rule in .checkpatch.conf


##############################
Test: GitLint - FAIL - 0.12 seconds
Run gitlint with rule in .gitlint
Bluetooth: call lock_sock() outside of spinlock section
11: B1 Line exceeds max length (85>80): "Fixes: e305509e678b3a4a ("Bluetooth: use correct lock to prevent UAF of hdev object")"


##############################
Test: BuildKernel - PASS - 542.37 seconds
Build Kernel with minimal configuration supports Bluetooth


##############################
Test: TestRunner: Setup - PASS - 358.20 seconds
Setup environment for running Test Runner


##############################
Test: TestRunner: l2cap-tester - PASS - 2.78 seconds
Run test-runner with l2cap-tester
Total: 40, Passed: 40 (100.0%), Failed: 0, Not Run: 0

##############################
Test: TestRunner: bnep-tester - PASS - 1.91 seconds
Run test-runner with bnep-tester
Total: 1, Passed: 1 (100.0%), Failed: 0, Not Run: 0

##############################
Test: TestRunner: mgmt-tester - FAIL - 33.12 seconds
Run test-runner with mgmt-tester
Total: 446, Passed: 436 (97.8%), Failed: 5, Not Run: 5

Failed Test Cases
Read Ext Controller Info 1                           Failed       0.028 seconds
Read Ext Controller Info 2                           Failed       0.028 seconds
Read Ext Controller Info 3                           Failed       0.028 seconds
Read Ext Controller Info 4                           Failed       0.020 seconds
Read Ext Controller Info 5                           Failed       0.024 seconds

##############################
Test: TestRunner: rfcomm-tester - PASS - 2.30 seconds
Run test-runner with rfcomm-tester
Total: 9, Passed: 9 (100.0%), Failed: 0, Not Run: 0

##############################
Test: TestRunner: sco-tester - PASS - 2.07 seconds
Run test-runner with sco-tester
Total: 8, Passed: 8 (100.0%), Failed: 0, Not Run: 0

##############################
Test: TestRunner: smp-tester - PASS - 2.25 seconds
Run test-runner with smp-tester
Total: 8, Passed: 8 (100.0%), Failed: 0, Not Run: 0

##############################
Test: TestRunner: userchan-tester - PASS - 2.08 seconds
Run test-runner with userchan-tester
Total: 3, Passed: 3 (100.0%), Failed: 0, Not Run: 0



---
Regards,
Linux Bluetooth

Patch

diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
index eed0dd066e12..64e54ab0892f 100644
--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -759,19 +759,39 @@  void hci_sock_dev_event(struct hci_dev *hdev, int event)
 	if (event == HCI_DEV_UNREG) {
 		struct sock *sk;
 
+restart:
 		/* Detach sockets from device */
 		read_lock(&hci_sk_list.lock);
 		sk_for_each(sk, &hci_sk_list.head) {
+			/* hci_sk_list.lock is preventing hci_sock_release()
+			 * from calling bt_sock_unlink().
+			 */
+			if (hci_pi(sk)->hdev != hdev || sk_unhashed(sk))
+				continue;
+			/* Take a ref because we can't call lock_sock() with
+			 * hci_sk_list.lock held.
+			 */
+			sock_hold(sk);
+			read_unlock(&hci_sk_list.lock);
 			lock_sock(sk);
-			if (hci_pi(sk)->hdev == hdev) {
+			/* Since hci_sock_release() might have already called
+			 * bt_sock_unlink() while waiting for lock_sock(),
+			 * use sk_hashed(sk) for checking that bt_sock_unlink()
+			 * is not yet called.
+			 */
+			if (sk_hashed(sk) && hci_pi(sk)->hdev == hdev) {
 				hci_pi(sk)->hdev = NULL;
 				sk->sk_err = EPIPE;
 				sk->sk_state = BT_OPEN;
 				sk->sk_state_change(sk);
-
 				hci_dev_put(hdev);
 			}
 			release_sock(sk);
+			sock_put(sk);
+			/* Restarting is safe, for hci_pi(sk)->hdev is now NULL
+			 * if condition met and will "continue;" otherwise.
+			 */
+			goto restart;
 		}
 		read_unlock(&hci_sk_list.lock);
 	}