syzbot reported a corrupted list in hci_chan_del. [1] Use hci dev lock to protect the reference count of conn to avoid race conditions on l2cap_sock_shutdown and l2cap_connect_cfm paths. The get/put actions of conn are unbalanced due to abnormal exit, so remove the redundant get/put actions of conn in l2cap_recv_acldata(). [1] kernel BUG at lib/list_debug.c:61! Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 1 UID: 0 PID: 5896 Comm: syz-executor213 Not tainted 6.14.0-rc1-next-20250204-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024 RIP: 0010:__list_del_entry_valid_or_report+0x12c/0x190 lib/list_debug.c:59 Code: 8c 4c 89 fe 48 89 da e8 32 8c 37 fc 90 0f 0b 48 89 df e8 27 9f 14 fd 48 c7 c7 a0 c0 60 8c 4c 89 fe 48 89 da e8 15 8c 37 fc 90 <0f> 0b 4c 89 e7 e8 0a 9f 14 fd 42 80 3c 2b 00 74 08 4c 89 e7 e8 cb RSP: 0018:ffffc90003f6f998 EFLAGS: 00010246 RAX: 000000000000004e RBX: dead000000000122 RCX: 01454d423f7fbf00 RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 RBP: dffffc0000000000 R08: ffffffff819f077c R09: 1ffff920007eded0 R10: dffffc0000000000 R11: fffff520007eded1 R12: dead000000000122 R13: dffffc0000000000 R14: ffff8880352248d8 R15: ffff888021297e00 FS: 00007f7ace6686c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f7aceeeb1d0 CR3: 000000003527c000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> __list_del_entry_valid include/linux/list.h:124 [inline] __list_del_entry include/linux/list.h:215 [inline] list_del_rcu include/linux/rculist.h:168 [inline] hci_chan_del+0x70/0x1b0 net/bluetooth/hci_conn.c:2858 l2cap_conn_free net/bluetooth/l2cap_core.c:1816 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_conn_put+0x70/0xe0 net/bluetooth/l2cap_core.c:1830 l2cap_sock_shutdown+0xa8a/0x1020 net/bluetooth/l2cap_sock.c:1377 l2cap_sock_release+0x79/0x1d0 net/bluetooth/l2cap_sock.c:1416 __sock_release net/socket.c:642 [inline] sock_close+0xbc/0x240 net/socket.c:1393 __fput+0x3e9/0x9f0 fs/file_table.c:448 task_work_run+0x24f/0x310 kernel/task_work.c:227 ptrace_notify+0x2d2/0x380 kernel/signal.c:2522 ptrace_report_syscall include/linux/ptrace.h:415 [inline] ptrace_report_syscall_exit include/linux/ptrace.h:477 [inline] syscall_exit_work+0xc7/0x1d0 kernel/entry/common.c:173 syscall_exit_to_user_mode_prepare kernel/entry/common.c:200 [inline] __syscall_exit_to_user_mode_work kernel/entry/common.c:205 [inline] syscall_exit_to_user_mode+0x24a/0x340 kernel/entry/common.c:218 do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f Reported-by: syzbot+10bd8fe6741eedd2be2e@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://syzkaller.appspot.com/bug?extid=10bd8fe6741eedd2be2e Tested-by: syzbot+10bd8fe6741eedd2be2e@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx> --- net/bluetooth/l2cap_core.c | 4 ---- net/bluetooth/l2cap_sock.c | 7 +++++-- 2 files changed, 5 insertions(+), 6 deletions(-) diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index adb8c33ac595..503626f70be5 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -7497,8 +7497,6 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags) if (!conn) conn = l2cap_conn_add(hcon); - conn = l2cap_conn_hold_unless_zero(conn); - hci_dev_unlock(hcon->hdev); if (!conn) @@ -7592,8 +7590,6 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags) break; } - l2cap_conn_put(conn); - drop: kfree_skb(skb); } diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index 46ea0bee2259..2a99394925a5 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -1359,10 +1359,12 @@ static int l2cap_sock_shutdown(struct socket *sock, int how) l2cap_chan_lock(chan); conn = chan->conn; - if (conn) + l2cap_chan_unlock(chan); + if (conn) { + hci_dev_lock(conn->hcon->hdev); /* prevent conn structure from being freed */ l2cap_conn_get(conn); - l2cap_chan_unlock(chan); + } if (conn) /* mutex lock must be taken before l2cap_chan_lock() */ @@ -1375,6 +1377,7 @@ static int l2cap_sock_shutdown(struct socket *sock, int how) if (conn) { mutex_unlock(&conn->chan_lock); l2cap_conn_put(conn); + hci_dev_unlock(conn->hcon->hdev); } lock_sock(sk); -- 2.43.0
