There is an imbalance in the rfcomm_session_hold / rfcomm_session_put operations which causes the following crash: [ 685.010159] BUG: unable to handle kernel paging request at 6b6b6b6b [ 685.010169] IP: [<c149d76d>] rfcomm_process_dlcs+0x1b/0x15e [ 685.010181] *pdpt = 000000002d665001 *pde = 0000000000000000 [ 685.010191] Oops: 0000 [#1] PREEMPT SMP [ 685.010247] [ 685.010255] Pid: 947, comm: krfcommd Tainted: G C 3.0.16-mid8-dirty #44 [ 685.010266] EIP: 0060:[<c149d76d>] EFLAGS: 00010246 CPU: 1 [ 685.010274] EIP is at rfcomm_process_dlcs+0x1b/0x15e [ 685.010281] EAX: e79f551c EBX: 6b6b6b6b ECX: 00000007 EDX: e79f40b4 [ 685.010288] ESI: e79f4060 EDI: ed4e1f70 EBP: ed4e1f68 ESP: ed4e1f50 [ 685.010295] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 [ 685.010303] Process krfcommd (pid: 947, ti=ed4e0000 task=ed43e5e0 task.ti=ed4e0000) [ 685.010308] Stack: [ 685.010312] ed4e1f68 c149eb53 e5925150 e79f4060 ed500000 ed4e1f70 ed4e1f80 c149ec10 [ 685.010331] 00000000 ed43e5e0 00000000 ed4e1f90 ed4e1f9c c149ec87 0000bf54 00000000 [ 685.010348] 00000000 ee03bf54 c149ec37 ed4e1fe4 c104fe01 00000000 00000000 00000000 [ 685.010367] Call Trace: [ 685.010376] [<c149eb53>] ? rfcomm_process_rx+0x6e/0x74 [ 685.010387] [<c149ec10>] rfcomm_process_sessions+0xb7/0xde [ 685.010398] [<c149ec87>] rfcomm_run+0x50/0x6d [ 685.010409] [<c149ec37>] ? rfcomm_process_sessions+0xde/0xde [ 685.010419] [<c104fe01>] kthread+0x63/0x68 [ 685.010431] [<c104fd9e>] ? __init_kthread_worker+0x42/0x42 [ 685.010442] [<c14dae82>] kernel_thread_helper+0x6/0xd This issue has been brought up earlier here: https://lkml.org/lkml/2011/5/21/127 The issue appears to be the rfcomm_session_put in rfcomm_recv_ua. This operation doesn't seem be to required as for the non-initiator case we have the rfcomm_process_rx doing an explicit put and in the initiator case the last dlc_unlink will drive the reference counter to 0. There have been several attempts to fix these issue: 6c2718d Bluetooth: Do not call rfcomm_session_put() for RFCOMM UA on closed socket 683d949 Bluetooth: Never deallocate a session when some DLC points to it but AFAICS they do not fix the issue just make it harder to reproduce. Signed-off-by: Octavian Purdila <octavian.purdila@xxxxxxxxx> Signed-off-by: Gopala Krishna Murala <gopala.krishna.murala@xxxxxxxxx> CC: Nick Pelly <npelly@xxxxxxxxxx> CC: Lukáš Turek <8an@xxxxxxxxxxx> CC: Marcel Holtmann <marcel@xxxxxxxxxxxx> CC: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> --- Changes from v1: * remove the gerrit Change-Id tag from the commit message * rephrase the comment for clarity and fix a few spelling errors Here is a full log of the hold/put operations which leads to the crash, where the x in hold(x) / put(x) is the reference counter value for the session before the hold/put operation: [ 75.332972] rfcomm_session_del: bt dump ed3cc580 [ 75.332991] hold(0) 0xc149d3f2 rfcomm_accept_connection+0x65/0x99 [ 75.333042] hold(0) 0xc149eb92 rfcomm_process_sessions+0x91/0xde [ 75.333074] hold(0) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.333101] hold(0) 0xc104fe01 kthread+0x63/0x68 [ 75.333134] hold(0) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.333166] [ 75.333179] hold(1) 0xc149eb9b rfcomm_process_sessions+0x9a/0xde [ 75.333210] hold(1) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.333238] hold(1) 0xc104fe01 kthread+0x63/0x68 [ 75.333266] hold(1) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.333293] [ 75.333306] put(2) 0xc149ebbf rfcomm_process_sessions+0xbe/0xde [ 75.333336] put(2) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.333363] put(2) 0xc104fe01 kthread+0x63/0x68 [ 75.333392] put(2) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.333419] [ 75.333432] hold(1) 0xc149eb9b rfcomm_process_sessions+0x9a/0xde [ 75.333461] hold(1) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.333489] hold(1) 0xc104fe01 kthread+0x63/0x68 [ 75.333517] hold(1) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.333544] [ 75.333558] put(2) 0xc149ebbf rfcomm_process_sessions+0xbe/0xde [ 75.333587] put(2) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.333615] put(2) 0xc104fe01 kthread+0x63/0x68 [ 75.333643] put(2) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.333671] [ 75.333683] hold(1) 0xc149eb9b rfcomm_process_sessions+0x9a/0xde [ 75.333713] hold(1) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.333741] hold(1) 0xc104fe01 kthread+0x63/0x68 [ 75.333769] hold(1) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.333796] [ 75.333808] hold(2) 0xc149dc9f rfcomm_dlc_link+0xe/0x36 [ 75.333837] hold(2) 0xc149e361 rfcomm_recv_mcc+0x279/0x5f7 [ 75.333866] hold(2) 0xc149ea64 rfcomm_recv_frame+0x385/0x3ae [ 75.333959] hold(2) 0xc149eacc rfcomm_process_rx+0x3f/0x74 [ 75.333988] hold(2) 0xc149ebb1 rfcomm_process_sessions+0xb0/0xde [ 75.334018] hold(2) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.334045] hold(2) 0xc104fe01 kthread+0x63/0x68 [ 75.334074] hold(2) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.334102] [ 75.334115] put(3) 0xc149ebbf rfcomm_process_sessions+0xbe/0xde [ 75.334145] put(3) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.334173] put(3) 0xc104fe01 kthread+0x63/0x68 [ 75.334201] put(3) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.334228] [ 75.334241] hold(2) 0xc149eb9b rfcomm_process_sessions+0x9a/0xde [ 75.334271] hold(2) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.334299] hold(2) 0xc104fe01 kthread+0x63/0x68 [ 75.334327] hold(2) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.334354] [ 75.334367] put(3) 0xc149ebbf rfcomm_process_sessions+0xbe/0xde [ 75.334397] put(3) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.334424] put(3) 0xc104fe01 kthread+0x63/0x68 [ 75.334453] put(3) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.334480] [ 75.334493] hold(2) 0xc149d8e1 rfcomm_security_cfm+0x35/0x10e [ 75.334523] hold(2) 0xc148dcb3 hci_encrypt_cfm+0x8f/0xaa [ 75.334556] hold(2) 0xc148f900 hci_event_packet+0x34e/0x10be [ 75.334584] hold(2) 0xc148aa06 hci_rx_task+0xab/0x205 [ 75.334615] hold(2) 0xc103bbc1 tasklet_action+0x6b/0xab [ 75.334645] hold(2) 0xc103c2b6 __do_softirq+0xdc/0x1dd [ 75.334670] [ 75.334683] put(3) 0xc149d9ac rfcomm_security_cfm+0x100/0x10e [ 75.334712] put(3) 0xc148dcb3 hci_encrypt_cfm+0x8f/0xaa [ 75.334743] put(3) 0xc148f900 hci_event_packet+0x34e/0x10be [ 75.334772] put(3) 0xc148aa06 hci_rx_task+0xab/0x205 [ 75.334801] put(3) 0xc103bbc1 tasklet_action+0x6b/0xab [ 75.334830] put(3) 0xc103c2b6 __do_softirq+0xdc/0x1dd [ 75.334854] [ 75.334867] hold(2) 0xc149eb9b rfcomm_process_sessions+0x9a/0xde [ 75.334984] hold(2) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.335012] hold(2) 0xc104fe01 kthread+0x63/0x68 [ 75.335042] hold(2) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.335070] [ 75.335082] put(3) 0xc149ebbf rfcomm_process_sessions+0xbe/0xde [ 75.335112] put(3) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.335141] put(3) 0xc104fe01 kthread+0x63/0x68 [ 75.335169] put(3) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.335195] [ 75.335209] hold(2) 0xc149eb9b rfcomm_process_sessions+0x9a/0xde [ 75.335239] hold(2) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.335266] hold(2) 0xc104fe01 kthread+0x63/0x68 [ 75.335295] hold(2) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.335322] [ 75.335335] put(3) 0xc149ebbf rfcomm_process_sessions+0xbe/0xde [ 75.335364] put(3) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.335392] put(3) 0xc104fe01 kthread+0x63/0x68 [ 75.335420] put(3) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.335447] [ 75.335460] hold(2) 0xc149eb9b rfcomm_process_sessions+0x9a/0xde [ 75.335490] hold(2) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.335517] hold(2) 0xc104fe01 kthread+0x63/0x68 [ 75.335545] hold(2) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.335573] [ 75.335586] put(3) 0xc149ebbf rfcomm_process_sessions+0xbe/0xde [ 75.335615] put(3) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.335643] put(3) 0xc104fe01 kthread+0x63/0x68 [ 75.335671] put(3) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.335698] [ 75.335711] hold(2) 0xc149eb9b rfcomm_process_sessions+0x9a/0xde [ 75.335741] hold(2) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.335769] hold(2) 0xc104fe01 kthread+0x63/0x68 [ 75.335797] hold(2) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.335825] [ 75.335837] put(3) 0xc149ebbf rfcomm_process_sessions+0xbe/0xde [ 75.335867] put(3) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.335958] put(3) 0xc104fe01 kthread+0x63/0x68 [ 75.335988] put(3) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.336016] [ 75.336029] hold(2) 0xc149eb9b rfcomm_process_sessions+0x9a/0xde [ 75.336058] hold(2) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.336086] hold(2) 0xc104fe01 kthread+0x63/0x68 [ 75.336114] hold(2) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.336141] [ 75.336154] hold(3) 0xc149d462 rfcomm_session_set_timer+0x3c/0x5c [ 75.336184] hold(3) 0xc149d55e rfcomm_dlc_unlink+0x3f/0x4a [ 75.336213] hold(3) 0xc149d715 __rfcomm_dlc_close+0x1ac/0x1b5 [ 75.336242] hold(3) 0xc149da76 rfcomm_recv_ua+0xbc/0x166 [ 75.336270] hold(3) 0xc149e922 rfcomm_recv_frame+0x243/0x3ae [ 75.336299] hold(3) 0xc149eacc rfcomm_process_rx+0x3f/0x74 [ 75.336328] hold(3) 0xc149ebb1 rfcomm_process_sessions+0xb0/0xde [ 75.336358] hold(3) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.336385] hold(3) 0xc104fe01 kthread+0x63/0x68 [ 75.336413] hold(3) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.336441] [ 75.336454] put(4) 0xc149d565 rfcomm_dlc_unlink+0x46/0x4a [ 75.336482] put(4) 0xc149d715 __rfcomm_dlc_close+0x1ac/0x1b5 [ 75.336512] put(4) 0xc149da76 rfcomm_recv_ua+0xbc/0x166 [ 75.336540] put(4) 0xc149e922 rfcomm_recv_frame+0x243/0x3ae [ 75.336569] put(4) 0xc149eacc rfcomm_process_rx+0x3f/0x74 [ 75.336597] put(4) 0xc149ebb1 rfcomm_process_sessions+0xb0/0xde [ 75.336628] put(4) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.336655] put(4) 0xc104fe01 kthread+0x63/0x68 [ 75.336684] put(4) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.336711] [ 75.336724] put(3) 0xc149ebbf rfcomm_process_sessions+0xbe/0xde [ 75.336753] put(3) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.336781] put(3) 0xc104fe01 kthread+0x63/0x68 [ 75.336809] put(3) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.336836] [ 75.336849] hold(2) 0xc149eb9b rfcomm_process_sessions+0x9a/0xde [ 75.336939] hold(2) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.336968] hold(2) 0xc104fe01 kthread+0x63/0x68 [ 75.336996] hold(2) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.337024] [ 75.337037] put(3) 0xc149db16 rfcomm_recv_ua+0x15c/0x166 [ 75.337067] put(3) 0xc149e922 rfcomm_recv_frame+0x243/0x3ae [ 75.337095] put(3) 0xc149eacc rfcomm_process_rx+0x3f/0x74 [ 75.337124] put(3) 0xc149ebb1 rfcomm_process_sessions+0xb0/0xde [ 75.337153] put(3) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.337180] put(3) 0xc104fe01 kthread+0x63/0x68 [ 75.337209] put(3) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.337236] [ 75.337249] put(2) 0xc149ebbf rfcomm_process_sessions+0xbe/0xde [ 75.337278] put(2) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.337306] put(2) 0xc104fe01 kthread+0x63/0x68 [ 75.337334] put(2) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.337361] [ 75.337374] hold(1) 0xc149eb9b rfcomm_process_sessions+0x9a/0xde [ 75.337404] hold(1) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.337432] hold(1) 0xc104fe01 kthread+0x63/0x68 [ 75.337460] hold(1) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.337487] [ 75.337500] put(2) 0xc149eaee rfcomm_process_rx+0x61/0x74 [ 75.337528] put(2) 0xc149ebb1 rfcomm_process_sessions+0xb0/0xde [ 75.337558] put(2) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.337586] put(2) 0xc104fe01 kthread+0x63/0x68 [ 75.337614] put(2) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.337641] [ 75.337653] hold(1) 0xc149e000 rfcomm_session_close+0x13/0x5b [ 75.337683] hold(1) 0xc149eafb rfcomm_process_rx+0x6e/0x74 [ 75.337711] hold(1) 0xc149ebb1 rfcomm_process_sessions+0xb0/0xde [ 75.337741] hold(1) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.337769] hold(1) 0xc104fe01 kthread+0x63/0x68 [ 75.337796] hold(1) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.337824] [ 75.337837] put(2) 0xc149db3f rfcomm_session_clear_timer+0x1f/0x22 [ 75.337867] put(2) 0xc149e03b rfcomm_session_close+0x4e/0x5b [ 75.337953] put(2) 0xc149eafb rfcomm_process_rx+0x6e/0x74 [ 75.337982] put(2) 0xc149ebb1 rfcomm_process_sessions+0xb0/0xde [ 75.338012] put(2) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.338040] put(2) 0xc104fe01 kthread+0x63/0x68 [ 75.338068] put(2) 0xc14dae42 kernel_thread_helper+0x6/0xd [ 75.338096] [ 75.338109] put(1) 0xc149e042 rfcomm_session_close+0x55/0x5b [ 75.338138] put(1) 0xc149eafb rfcomm_process_rx+0x6e/0x74 [ 75.338167] put(1) 0xc149ebb1 rfcomm_process_sessions+0xb0/0xde [ 75.338197] put(1) 0xc149ec2f rfcomm_run+0x50/0x6d [ 75.338224] put(1) 0xc104fe01 kthread+0x63/0x68 [ 75.338252] put(1) 0xc14dae42 kernel_thread_helper+0x6/0xd net/bluetooth/rfcomm/core.c | 18 ++++++++++++------ 1 files changed, 12 insertions(+), 6 deletions(-) diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c index 501649b..8a60238 100644 --- a/net/bluetooth/rfcomm/core.c +++ b/net/bluetooth/rfcomm/core.c @@ -1164,12 +1164,18 @@ static int rfcomm_recv_ua(struct rfcomm_session *s, u8 dlci) break; case BT_DISCONN: - /* When socket is closed and we are not RFCOMM - * initiator rfcomm_process_rx already calls - * rfcomm_session_put() */ - if (s->sock->sk->sk_state != BT_CLOSED) - if (list_empty(&s->dlcs)) - rfcomm_session_put(s); + /* rfcomm_session_put is called later so don't do + * anything here otherwise we will mess up the session + * reference counter: + * + * (a) when we are the initiator dlc_unlink will drive + * the reference counter to 0 (there is no initial put + * after session_add) + * + * (b) when we are not the initiator rfcomm_rx_process + * will explicitly call put to balance the initial hold + * done after session add. + */ break; } } -- 1.7.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
