[RFC] Bluetooth: L2CAP: Fix general protection fault in l2cap_chan_timeout

Commit Message

Luiz Augusto von Dentz June 2, 2021, 11:23 p.m. UTC

From: Luiz Augusto von Dentz <[e-mail]>

Even though l2cap_chan_del calls __clear_chan_timer that uses
cancel_delayed_work which doesn't prevent the work to run as it could be
already pending.

So instead this check if chan->conn has been set to NULL, which indicates
that l2cap_conn_del might have run, and proceed to release its reference
since the channel has already been cleanup.

Reported-by: [e-mail]
Signed-off-by: Luiz Augusto von Dentz <[e-mail]>
---
 net/bluetooth/l2cap_core.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Comments

[e-mail] June 2, 2021, 11:47 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=492905

---Test result---

Test Summary:
CheckPatch                    PASS      0.47 seconds
GitLint                       PASS      0.11 seconds
BuildKernel                   PASS      507.46 seconds
TestRunner: Setup             PASS      327.25 seconds
TestRunner: l2cap-tester      PASS      2.50 seconds
TestRunner: bnep-tester       PASS      1.86 seconds
TestRunner: mgmt-tester       PASS      27.38 seconds
TestRunner: rfcomm-tester     PASS      2.01 seconds
TestRunner: sco-tester        PASS      2.00 seconds
TestRunner: smp-tester        PASS      2.02 seconds
TestRunner: userchan-tester   PASS      1.95 seconds

Details
##############################
Test: CheckPatch - PASS - 0.47 seconds
Run checkpatch.pl script with rule in .checkpatch.conf


##############################
Test: GitLint - PASS - 0.11 seconds
Run gitlint with rule in .gitlint


##############################
Test: BuildKernel - PASS - 507.46 seconds
Build Kernel with minimal configuration supports Bluetooth


##############################
Test: TestRunner: Setup - PASS - 327.25 seconds
Setup environment for running Test Runner


##############################
Test: TestRunner: l2cap-tester - PASS - 2.50 seconds
Run test-runner with l2cap-tester
Total: 40, Passed: 40 (100.0%), Failed: 0, Not Run: 0

##############################
Test: TestRunner: bnep-tester - PASS - 1.86 seconds
Run test-runner with bnep-tester
Total: 1, Passed: 1 (100.0%), Failed: 0, Not Run: 0

##############################
Test: TestRunner: mgmt-tester - PASS - 27.38 seconds
Run test-runner with mgmt-tester
Total: 446, Passed: 433 (97.1%), Failed: 0, Not Run: 13

##############################
Test: TestRunner: rfcomm-tester - PASS - 2.01 seconds
Run test-runner with rfcomm-tester
Total: 9, Passed: 9 (100.0%), Failed: 0, Not Run: 0

##############################
Test: TestRunner: sco-tester - PASS - 2.00 seconds
Run test-runner with sco-tester
Total: 8, Passed: 8 (100.0%), Failed: 0, Not Run: 0

##############################
Test: TestRunner: smp-tester - PASS - 2.02 seconds
Run test-runner with smp-tester
Total: 8, Passed: 8 (100.0%), Failed: 0, Not Run: 0

##############################
Test: TestRunner: userchan-tester - PASS - 1.95 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/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 9ebb85df4db4..4408e07a00d1 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -414,11 +414,21 @@  static void l2cap_chan_timeout(struct work_struct *work)
 {
 	struct l2cap_chan *chan = container_of(work, struct l2cap_chan,
 					       chan_timer.work);
-	struct l2cap_conn *conn = chan->conn;
+	struct l2cap_conn *conn;
 	int reason;
 
 	BT_DBG("chan %p state %s", chan, state_to_string(chan->state));
 
+	conn = chan->conn;
+	if (!conn) {
+		/* Channel is no longer attached to a connection so
+		 * l2cap_conn_del might have run, just release reference
+		 * acquired via __set_chan_timer.
+		 */
+		l2cap_chan_put(chan);
+		return;
+	}
+
 	mutex_lock(&conn->chan_lock);
 	/* __set_chan_timer() calls l2cap_chan_hold(chan) while scheduling
 	 * this work. No need to call l2cap_chan_hold(chan) here again.