diff options
| author | Octavian Purdila <octavian.purdila@intel.com> | 2012-01-27 18:32:39 +0100 |
|---|---|---|
| committer | Johan Hedberg <johan.hedberg@intel.com> | 2012-02-15 12:09:26 +0100 |
| commit | cf33e77b76d7439f21a23a94eab4ab3b405a6a7d (patch) | |
| tree | 3e8ad4b4c7a2cb23835c3c2144457a56eba7129b /net/bluetooth/rfcomm | |
| parent | Bluetooth: Fix potential deadlock (diff) | |
| download | linux-cf33e77b76d7439f21a23a94eab4ab3b405a6a7d.tar.xz linux-cf33e77b76d7439f21a23a94eab4ab3b405a6a7d.zip | |
Bluetooth: Fix RFCOMM session reference counting issue
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@intel.com>
Signed-off-by: Gopala Krishna Murala <gopala.krishna.murala@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Diffstat (limited to 'net/bluetooth/rfcomm')
| -rw-r--r-- | 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 501649bf5596..8a602388f1e7 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; } } |