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Bluetooth: Fix null-ptr-deref in l2cap_sock_resume_cb()

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[ Upstream commit a0075accbf0d76c2dad1ad3993d2e944505d99a0 ]

syzbot reported null-ptr-deref in l2cap_sock_resume_cb(). [0]

l2cap_sock_resume_cb() has a similar problem that was fixed by commit
1bff51ea59 ("Bluetooth: fix use-after-free error in lock_sock_nested()").

Since both l2cap_sock_kill() and l2cap_sock_resume_cb() are executed
under l2cap_sock_resume_cb(), we can avoid the issue simply by checking
if chan->data is NULL.

Let's not access to the killed socket in l2cap_sock_resume_cb().

[0]:
BUG: KASAN: null-ptr-deref in instrument_atomic_write include/linux/instrumented.h:82 [inline]
BUG: KASAN: null-ptr-deref in clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline]
BUG: KASAN: null-ptr-deref in l2cap_sock_resume_cb+0xb4/0x17c net/bluetooth/l2cap_sock.c:1711
Write of size 8 at addr 0000000000000570 by task kworker/u9:0/52

CPU: 1 UID: 0 PID: 52 Comm: kworker/u9:0 Not tainted 6.16.0-rc4-syzkaller-g7482bb149b9f #0 PREEMPT
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: hci0 hci_rx_work
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:501 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 print_report+0x58/0x84 mm/kasan/report.c:524
 kasan_report+0xb0/0x110 mm/kasan/report.c:634
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x264/0x2a4 mm/kasan/generic.c:189
 __kasan_check_write+0x20/0x30 mm/kasan/shadow.c:37
 instrument_atomic_write include/linux/instrumented.h:82 [inline]
 clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline]
 l2cap_sock_resume_cb+0xb4/0x17c net/bluetooth/l2cap_sock.c:1711
 l2cap_security_cfm+0x524/0xea0 net/bluetooth/l2cap_core.c:7357
 hci_auth_cfm include/net/bluetooth/hci_core.h:2092 [inline]
 hci_auth_complete_evt+0x2e8/0xa4c net/bluetooth/hci_event.c:3514
 hci_event_func net/bluetooth/hci_event.c:7511 [inline]
 hci_event_packet+0x650/0xe9c net/bluetooth/hci_event.c:7565
 hci_rx_work+0x320/0xb18 net/bluetooth/hci_core.c:4070
 process_one_work+0x7e8/0x155c kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3402
 kthread+0x5fc/0x75c kernel/kthread.c:464
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:847

Fixes: d97c899bde ("Bluetooth: Introduce L2CAP channel callback for resuming")
Reported-by: syzbot+e4d73b165c3892852d22@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/686c12bd.a70a0220.29fe6c.0b13.GAE@google.com/
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Kuniyuki Iwashima
2025-07-07 19:28:29 +00:00
committed by Greg Kroah-Hartman
parent 5dd6a44174
commit c4f16f6b07
1 changed files with 3 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
net/bluetooth/l2cap_sock.c
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@@ -1687,6 +1687,9 @@ static void l2cap_sock_resume_cb(struct l2cap_chan *chan)
{
struct sock *sk = chan->data;
if (!sk)
return;
if (test_and_clear_bit(FLAG_PENDING_SECURITY, &chan->flags)) {
sk->sk_state = BT_CONNECTED;
chan->state = BT_CONNECTED;