Re: kernel panic happens when disconnecting Bluetooth headset
flat view
From: Lan Zhu <hidden>
Date: 2009-09-11 15:28:20
Hi Marcel, 2009/9/11 Marcel Holtmann [off-list ref]:
quoted hunk ↗ jump to hunk
Hi Zhu,quoted
We met a issue that kernel panic happens when disconnecting some kinds of Bluetooth headset, then we did some analysis and made some changes on kernel code which have avoided the panic happening. Would you please help to check if our analysis and fix is correct? ============= Issue description ============= On Android platform(kernel 2.6.29), disconnecting Bluetooth headset may cause kernel panic on certain conditions. (Pre-condition is android paired with headset.) Initiate the connection from android, disconnect it from android, result is OK. Initiate the connection from android, disconnect it from headset, result is OK. Initiate the connection from headset, disconnect it from headset, result is OK. Initiate the connection from headset, disconnect it from android, for Motorola H12 headset, result is OK. Initiate the connection from headset, disconnect it from android, for Motorola H620/560 headset, result is kernel panic. ============= Kernel panic point ============= kernel panic at __list_del() in the function rfcomm_session_del() , panic reason is "Unable to handle kernel paging request at virtual address 00200200" ============= Kernel log analysis ============= rfcomm_session_del() is still called after the session entry is removed from the list. Then __list_del() will cause kernel panic because of the incorrect pointer. This situation occurs when calling rfcomm_recv_ua() when the socket state is BT_CLOSED . So we need to find out why the socket state become BT_CLOSED before we calling rfcomm_recv_ua(). # [ 171.677429] rfcomm_sock_sendmsg: sock ce9a0960, sk cc5c4c00 [ 171.683532] rfcomm_dlc_send: dlc cd3fe920 mtu 255 len 14 [ 171.689422] rfcomm_process_rx: session cc751be0 state 1 qlen 0 [ 171.695709] rfcomm_process_rx: @@@ @@@ sk_state = 1 [ 171.701110] rfcomm_process_dlcs: session cc751be0 state 1 [ 171.706939] rfcomm_process_tx: dlc cd3fe920 state 1 cfc 40 rx_credits 33 tx_credits 31 [ 171.715515] rfcomm_send_frame: session cc751be0 len 18 [ 171.721130] rfcomm_session_put: in rfcomm_session_put, s->refcnt = 3 [ 174.127807] rfcomm_sock_sendmsg: sock ce9a0960, sk cc5c4c00 [ 174.134490] rfcomm_dlc_send: dlc cd3fe920 mtu 255 len 6 [ 174.141540] rfcomm_process_rx: session cc751be0 state 1 qlen 0 [ 174.148498] rfcomm_process_rx: @@@ @@@ sk_state = 1 [ 174.154968] rfcomm_process_dlcs: session cc751be0 state 1 [ 174.161437] rfcomm_process_tx: dlc cd3fe920 state 1 cfc 40 rx_credits 33 tx_credits 30 [ 174.171173] rfcomm_send_frame: session cc751be0 len 10 [ 174.177642] rfcomm_session_put: in rfcomm_session_put, s->refcnt = 3 [ 174.205932] rfcomm_sock_release: sock ce9a0960, sk cc5c4c00 [ 174.212707] rfcomm_sock_shutdown: sock ce9a0960, sk cc5c4c00 [ 174.220031] __rfcomm_sock_close: sk cc5c4c00 state 1 socket ce9a0960 [ 174.227508] __rfcomm_dlc_close: dlc cd3fe920 state 1 dlci 20 err 0 session cc751be0 [ 174.236877] rfcomm_send_disc: cc751be0 dlci 20 [ 174.242706] rfcomm_send_frame: session cc751be0 len 4 [ 174.248962] rfcomm_dlc_set_timer: dlc cd3fe920 state 8 timeout 2560 [ 174.256835] rfcomm_sock_kill: sk cc5c4c00 state 1 refcnt 2 [ 174.263336] rfcomm_sock_destruct: sk cc5c4c00 dlc cd3fe920 [ 174.399444] rfcomm_l2data_ready: ccf70400 bytes 4 [ 174.404724] rfcomm_process_rx: session cc751be0 state 1 qlen 1 [ 174.411010] rfcomm_process_rx: @@@ @@@ sk_state = 1 [ 174.416412] rfcomm_recv_ua: session cc751be0 state 1 dlci 20 [ 174.422515] __rfcomm_dlc_close: dlc cd3fe920 state 9 dlci 20 err 0 session cc751be0 [ 174.430816] rfcomm_dlc_clear_timer: dlc cd3fe920 state 9 [ 174.436553] rfcomm_dlc_unlink: dlc cd3fe920 refcnt 1 session cc751be0 [ 174.443572] rfcomm_dlc_free: cd3fe920 [ 174.447570] rfcomm_session_put: in rfcomm_session_put, s->refcnt = 3 [ 174.454528] rfcomm_send_disc: cc751be0 dlci 0 [ 174.459259] rfcomm_send_frame: session cc751be0 len 4 [ 174.464904] rfcomm_process_dlcs: session cc751be0 state 8 [ 174.470703] rfcomm_session_put: in rfcomm_session_put, s->refcnt = 2 [ 174.898284] rfcomm_l2data_ready: ccf70400 bytes 4 [ 174.903442] rfcomm_l2state_change: ccf70400 state 9 [ 174.908874] rfcomm_process_rx: session cc751be0 state 8 qlen 1 [ 174.915130] rfcomm_process_rx: @@@ @@@ sk_state = 9 [ 174.920562] rfcomm_recv_ua: session cc751be0 state 8 dlci 0 [ 174.926574] rfcomm_session_put: in rfcomm_session_put, s->refcnt = 2 [ 174.933532] rfcomm_process_rx: @@@ @@@ sk_state == BT_CLOSED , s->initiator=0 [ 174.941253] rfcomm_session_put: in rfcomm_session_put, s->refcnt = 1 [ 174.948211] rfcomm_session_del: session cc751be0 state 8 [ 174.953918] @@@@ in rfcomm_session_del() [ 174.958312] @@@@ s->list = cc751be0 [ 174.962097] @@@@ s->list.next = ccbfe9a0 [ 174.966369] @@@@ s->list.prev = c047d524 [ 174.970733] @@@@ list is valid, call list_del() [ 174.975646] @@@@ after list_del() [ 174.979278] @@@@ s->list = cc751be0 [ 174.983184] @@@@ s->list.next = 00100100 [ 174.987457] @@@@ s->list.prev = 00200200 [ 174.991729] rfcomm_session_close: session cc751be0 state 8 err 104 [ 174.998504] rfcomm_session_put: in rfcomm_session_put, s->refcnt = 1 [ 175.005310] rfcomm_session_del: session cc751be0 state 9 [ 175.011169] @@@@ in rfcomm_session_del() [ 175.015441] @@@@ s->list = cc751be0 [ 175.019409] @@@@ s->list.next = 00100100 [ 175.023651] @@@@ s->list.prev = 00200200 [ 175.027923] @@@@ list is valid, call list_del() [ 175.032958] Unable to handle kernel paging request at virtual address 00200200 [ 175.040679] pgd = c0004000 [ 175.043792] [00200200] *pgd=00000000 [ 175.047821] Internal error: Oops: 817 [#1] [ 175.052246] Modules linked in: [ 175.055725] CPU: 0 Not tainted (2.6.29-omap1-dirty #34) [ 175.061859] PC is at rfcomm_session_del+0x6c/0x108 [ 175.067047] LR is at release_console_sem+0x190/0x1a0 [ 175.072509] pc : [<c033ded8>] lr : [<c0066308>] psr: 60000013 [ 175.072509] sp : cc1abf38 ip : cc1abe68 fp : cc1abf4c [ 175.084960] r10: cc751c04 r9 : c036d2fc r8 : cc751be0 [ 175.090545] r7 : 00000068 r6 : cc751c04 r5 : 00000009 r4 : cc751be0 [ 175.097656] r3 : 00100100 r2 : 00100100 r1 : 00200200 r0 : c0422876 ============= HCI log analysis ============= Compare the hcidump log of the correct case with the one of the panic case, we found there is only one difference in the message sequence. In the panic case, headset send L2CAP Disconn_Req immediately after sending rfcomm UA frame to android. We think this is the reason that cause the socket state become BT_CLOSED. Please compare these two log, pay attention to the message direction of the last Disconn_Req. Log of correct case: ---------------------------- 009-09-10 15:27:28.963519 < ACL data: handle 1 flags 0x02 dlen 22 L2CAP(d): cid 0x0047 len 18 [psm 3] RFCOMM(d): UIH: cr 0 dlci 20 pf 0 ilen 14 fcs 0xeb 0000: 0d 0a 2b 43 49 45 56 3a 20 37 2c 33 0d 0a ..+CIEV: 7,3.. 009-09-10 15:27:28.967272 > HCI Event: Number of Completed Packets (0x13) plen handle 1 packets 1 009-09-10 15:27:29.243945 < ACL data: handle 1 flags 0x02 dlen 8 L2CAP(d): cid 0x0047 len 4 [psm 3] RFCOMM(s): DISC: cr 0 dlci 20 pf 1 ilen 0 fcs 0x7d 009-09-10 15:27:29.247363 > HCI Event: Number of Completed Packets (0x13) plen handle 1 packets 1 009-09-10 15:27:29.274890 > ACL data: handle 1 flags 0x02 dlen 8 L2CAP(d): cid 0x0040 len 4 [psm 3] RFCOMM(s): UA: cr 0 dlci 20 pf 1 ilen 0 fcs 0x57 009-09-10 15:27:29.296343 < ACL data: handle 1 flags 0x02 dlen 8 L2CAP(d): cid 0x0047 len 4 [psm 3] RFCOMM(s): DISC: cr 0 dlci 0 pf 1 ilen 0 fcs 0x9c 009-09-10 15:27:29.298480 > HCI Event: Number of Completed Packets (0x13) plen handle 1 packets 1 009-09-10 15:27:29.319873 > ACL data: handle 1 flags 0x02 dlen 8 L2CAP(d): cid 0x0040 len 4 [psm 3] RFCOMM(s): UA: cr 0 dlci 0 pf 1 ilen 0 fcs 0xb6 009-09-10 15:27:29.320727 < ACL data: handle 1 flags 0x02 dlen 12 L2CAP(s): Disconn req: dcid 0x0047 scid 0x0040 009-09-10 15:27:29.323474 > HCI Event: Number of Completed Packets (0x13) plen handle 1 packets 1 009-09-10 15:27:29.337237 > ACL data: handle 1 flags 0x02 dlen 12 L2CAP(s): Disconn rsp: dcid 0x0047 scid 0x0040 log of panic case: ------------------------ 2009-09-10 13:34:24.020208 < ACL data: handle 1 flags 0x02 dlen 22 L2CAP(d): cid 0x0041 len 18 [psm 3] RFCOMM(d): UIH: cr 0 dlci 20 pf 0 ilen 14 fcs 0xeb 0000: 0d 0a 2b 43 49 45 56 3a 20 37 2c 33 0d 0a ..+CIEV: 7,3.. 2009-09-10 13:34:24.281256 > HCI Event: Number of Completed Packets (0x13) plen 5 handle 1 packets 1 2009-09-10 13:34:24.083580 < ACL data: handle 1 flags 0x02 dlen 8 L2CAP(d): cid 0x0041 len 4 [psm 3] RFCOMM(s): DISC: cr 0 dlci 20 pf 1 ilen 0 fcs 0x7d 2009-09-10 13:34:24.529442 > HCI Event: Number of Completed Packets (0x13) plen 5 handle 1 packets 1 2009-09-10 13:34:24.531914 > ACL data: handle 1 flags 0x02 dlen 8 L2CAP(d): cid 0x0040 len 4 [psm 3] RFCOMM(s): UA: cr 0 dlci 20 pf 1 ilen 0 fcs 0x57 2009-09-10 13:34:24.533135 < ACL data: handle 1 flags 0x02 dlen 8 L2CAP(d): cid 0x0041 len 4 [psm 3] RFCOMM(s): DISC: cr 0 dlci 0 pf 1 ilen 0 fcs 0x9c 2009-09-10 13:34:25.028649 > HCI Event: Number of Completed Packets (0x13) plen 5 handle 1 packets 1 2009-09-10 13:34:25.032128 > ACL data: handle 1 flags 0x02 dlen 8 L2CAP(d): cid 0x0040 len 4 [psm 3] RFCOMM(s): UA: cr 0 dlci 0 pf 1 ilen 0 fcs 0xb6 2009-09-10 13:34:25.032341 > ACL data: handle 1 flags 0x02 dlen 12 L2CAP(s): Disconn req: dcid 0x0040 scid 0x0041 2009-09-10 13:34:25.032646 < ACL data: handle 1 flags 0x02 dlen 12 L2CAP(s): Disconn rsp: dcid 0x0040 scid 0x0041 ============= Analysis Result ============= For some kinds of Bluetooth headset such as Motorola H560/H620 which are based on BCM2044S, they will send L2CAP Disconn_Req command right after sending rfcomm UA frame. This L2CAP Disconn_Req will cause the rfcomm socket state become BT_CLOSED before completely handling UA frame, thus it will cause kernel panic. I think we can ignore the received rfcomm frames if socket state is BT_CLOSED, because it doesn't make sense in the BT_CLOSED state. ============= Changed Code ============= We changed the code in the function rfcomm_process_rx() in net/bluetooth/rfcomm/core.c, check the socket state first before handling the received framew. If the socket state is BT_CLOSED, we don't handle any rfcomm frames but just close the session. The change is like below + if (sk->sk_state != BT_CLOSED) { /* Get data directly from socket receive queue without copying it. */ while ((skb = skb_dequeue(&sk->sk_receive_queue))) { skb_orphan(skb); rfcomm_recv_frame(s, skb); } - - if (sk->sk_state == BT_CLOSED) { + } else { if (!s->initiator) rfcomm_session_put(s); rfcomm_session_close(s, sk->sk_err); }so I do see the issue here, but I don't agree with the fix since it changes behavior that might cause other issues. So in case the frame processing leads to sk->sk_state == BT_CLOSED we are not closing the connection anymore if we make it depend on a state before the frame processing. And nothing guarantees that rfcomm_process_rx gets scheduled again.diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c index 94b3388..606143b 100644 --- a/net/bluetooth/rfcomm/core.c +++ b/net/bluetooth/rfcomm/core.c@@ -1798,12 +1798,16 @@ static inline void rfcomm_process_rx(struct rfcomm_session *s)BT_DBG("session %p state %ld qlen %d", s, s->state, skb_queue_len(&sk->sk_receive_queue)); + rfcomm_session_hold(s); + /* Get data directly from socket receive queue without copying it. */ while ((skb = skb_dequeue(&sk->sk_receive_queue))) { skb_orphan(skb); rfcomm_recv_frame(s, skb); } + rfcomm_session_put(s); + if (sk->sk_state == BT_CLOSED) { if (!s->initiator) rfcomm_session_put(s); What does the above patch do for you? Since if I read it correctly, then the rfcomm_recv_ua causes the rfcomm_session_put to trigger the closing of the session. And then in this case it is delayed until after all frames are processed.
I've tried your patch but unfortunately kernel panic still happened.
From the log I noticed that if rfcomm_l2state_change is called before
rfcomm_process_rx, kernel panic will happen definitely. Below lines are in the correct log, [ 139.323852] rfcomm_l2data_ready: ccf70000 bytes 4 [ 139.346252] rfcomm_process_rx: session ccb94ce0 state 8 qlen 1 ... [ 139.457519] rfcomm_l2state_change: ccf70000 state 9 (disconnect ok) In the above case, when process_rx, the code in the condition "if (sk->sk_state == BT_CLOSED)" will never run. Below lines are in the panic log, [ 174.898284] rfcomm_l2data_ready: ccf70400 bytes 4 [ 174.903442] rfcomm_l2state_change: ccf70400 state 9 [ 174.908874] rfcomm_process_rx: session cc751be0 state 8 qlen 1 ... ( then panic) In the above case, sk_state is changed to 9 (BT_CLOSED) firstly, then process_rx, so the code in the condition "if (sk->sk_state == BT_CLOSED) " will be run, it will call session_put twice. I think this is the root cause of panic. Thanks, Zhu Lan