| Message ID | 20210713162838.693266-1-desmondcheongzx@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] Bluetooth: fix inconsistent lock state in sco | expand |
This is automated email and please do not reply to this email! Dear submitter, Thank you for submitting the patches to the linux bluetooth mailing list. This is a CI test results with your patch series: PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=514869 ---Test result--- Test Summary: CheckPatch PASS 0.60 seconds GitLint PASS 0.10 seconds BuildKernel PASS 501.68 seconds TestRunner: Setup PASS 336.91 seconds TestRunner: l2cap-tester PASS 2.57 seconds TestRunner: bnep-tester PASS 1.93 seconds TestRunner: mgmt-tester PASS 29.64 seconds TestRunner: rfcomm-tester PASS 2.08 seconds TestRunner: sco-tester PASS 2.04 seconds TestRunner: smp-tester FAIL 2.12 seconds TestRunner: userchan-tester PASS 1.94 seconds Details ############################## Test: CheckPatch - PASS - 0.60 seconds Run checkpatch.pl script with rule in .checkpatch.conf ############################## Test: GitLint - PASS - 0.10 seconds Run gitlint with rule in .gitlint ############################## Test: BuildKernel - PASS - 501.68 seconds Build Kernel with minimal configuration supports Bluetooth ############################## Test: TestRunner: Setup - PASS - 336.91 seconds Setup environment for running Test Runner ############################## Test: TestRunner: l2cap-tester - PASS - 2.57 seconds Run test-runner with l2cap-tester Total: 40, Passed: 40 (100.0%), Failed: 0, Not Run: 0 ############################## Test: TestRunner: bnep-tester - PASS - 1.93 seconds Run test-runner with bnep-tester Total: 1, Passed: 1 (100.0%), Failed: 0, Not Run: 0 ############################## Test: TestRunner: mgmt-tester - PASS - 29.64 seconds Run test-runner with mgmt-tester Total: 446, Passed: 443 (99.3%), Failed: 0, Not Run: 3 ############################## Test: TestRunner: rfcomm-tester - PASS - 2.08 seconds Run test-runner with rfcomm-tester Total: 9, Passed: 9 (100.0%), Failed: 0, Not Run: 0 ############################## Test: TestRunner: sco-tester - PASS - 2.04 seconds Run test-runner with sco-tester Total: 8, Passed: 8 (100.0%), Failed: 0, Not Run: 0 ############################## Test: TestRunner: smp-tester - FAIL - 2.12 seconds Run test-runner with smp-tester Total: 8, Passed: 7 (87.5%), Failed: 1, Not Run: 0 Failed Test Cases SMP Client - SC Request 2 Failed 0.027 seconds ############################## Test: TestRunner: userchan-tester - PASS - 1.94 seconds Run test-runner with userchan-tester Total: 3, Passed: 3 (100.0%), Failed: 0, Not Run: 0 --- Regards, Linux Bluetooth
Hi Desmond, On Tue, Jul 13, 2021 at 9:29 AM Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> wrote: > > Syzbot reported an inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} lock > usage in sco_conn_del and sco_sock_timeout that could lead to > deadlocks. > > This inconsistent lock state can also happen in sco_conn_ready, > rfcomm_connect_ind, and bt_accept_enqueue. > > The issue is that these functions take a spin lock on the socket with > interrupts enabled, but sco_sock_timeout takes the lock in an IRQ > context. This could lead to deadlocks: > > CPU0 > ---- > lock(slock-AF_BLUETOOTH-BTPROTO_SCO); > <Interrupt> > lock(slock-AF_BLUETOOTH-BTPROTO_SCO); > > *** DEADLOCK *** > > We fix this by ensuring that local bh is disabled before calling > bh_lock_sock. > > After doing this, we additionally need to protect sco_conn_lock by > disabling local bh. > > This is necessary because sco_conn_del makes a call to sco_chan_del > while holding on to the sock lock, and sco_chan_del itself makes a > call to sco_conn_lock. If sco_conn_lock is held elsewhere with > interrupts enabled, there could still be a > slock-AF_BLUETOOTH-BTPROTO_SCO --> &conn->lock#2 lock inversion as > follows: > > CPU0 CPU1 > ---- ---- > lock(&conn->lock#2); > local_irq_disable(); > lock(slock-AF_BLUETOOTH-BTPROTO_SCO); > lock(&conn->lock#2); > <Interrupt> > lock(slock-AF_BLUETOOTH-BTPROTO_SCO); > > *** DEADLOCK *** > > As sco_conn_del now disables local bh before calling sco_chan_del, > instead of disabling local bh for the calls to sco_conn_lock in > sco_chan_del, we instead wrap other calls to sco_chan_del with > local_bh_disable/enable. > > Reported-by: syzbot+2f6d7c28bb4bf7e82060@syzkaller.appspotmail.com > Tested-by: syzbot+2f6d7c28bb4bf7e82060@syzkaller.appspotmail.com > Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> > --- > > Hi, > > The previous version of this patch was a bit of a mess, so I made the > following changes. > > v1 -> v2: > - Instead of pulling out the clean-up code out from sco_chan_del and > using it directly in sco_conn_del, disable local irqs for relevant > sections. > - Disable local irqs more thoroughly for instances of > bh_lock_sock/bh_lock_sock_nested in the bluetooth subsystem. > Specifically, the calls in af_bluetooth.c and rfcomm/sock.c are now made > with local irqs disabled as well. > > Best wishes, > Desmond > > net/bluetooth/rfcomm/sock.c | 2 ++ > net/bluetooth/sco.c | 26 +++++++++++++++++++++++++- > 2 files changed, 27 insertions(+), 1 deletion(-) > > diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c > index ae6f80730561..d8734abb2df4 100644 > --- a/net/bluetooth/rfcomm/sock.c > +++ b/net/bluetooth/rfcomm/sock.c > @@ -974,6 +974,7 @@ int rfcomm_connect_ind(struct rfcomm_session *s, u8 channel, struct rfcomm_dlc * > if (!parent) > return 0; > > + local_bh_disable(); > bh_lock_sock(parent); > > /* Check for backlog size */ > @@ -1002,6 +1003,7 @@ int rfcomm_connect_ind(struct rfcomm_session *s, u8 channel, struct rfcomm_dlc * > > done: > bh_unlock_sock(parent); > + local_bh_enable(); Looks like you are touching RFCOMM as well, perhaps you should have it split, also how about other sockets like L2CAP and HCI are they affected? There seems to be a lot of problem with the likes of bh_lock_sock I wonder if going with local_bh_disable is overall a better way to handle. > if (test_bit(BT_SK_DEFER_SETUP, &bt_sk(parent)->flags)) > parent->sk_state_change(parent); > diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c > index 3bd41563f118..2548b8f81473 100644 > --- a/net/bluetooth/sco.c > +++ b/net/bluetooth/sco.c > @@ -167,16 +167,22 @@ static void sco_conn_del(struct hci_conn *hcon, int err) > BT_DBG("hcon %p conn %p, err %d", hcon, conn, err); > > /* Kill socket */ > + local_bh_disable(); > sco_conn_lock(conn); > sk = conn->sk; > sco_conn_unlock(conn); > + local_bh_enable(); > > if (sk) { > sock_hold(sk); > + > + local_bh_disable(); > bh_lock_sock(sk); > sco_sock_clear_timer(sk); > sco_chan_del(sk, err); > bh_unlock_sock(sk); > + local_bh_enable(); > + > sco_sock_kill(sk); > sock_put(sk); > } > @@ -202,6 +208,7 @@ static int sco_chan_add(struct sco_conn *conn, struct sock *sk, > { > int err = 0; > > + local_bh_disable(); > sco_conn_lock(conn); > if (conn->sk) > err = -EBUSY; > @@ -209,6 +216,7 @@ static int sco_chan_add(struct sco_conn *conn, struct sock *sk, > __sco_chan_add(conn, sk, parent); > > sco_conn_unlock(conn); > + local_bh_enable(); > return err; > } > > @@ -303,9 +311,11 @@ static void sco_recv_frame(struct sco_conn *conn, struct sk_buff *skb) > { > struct sock *sk; > > + local_bh_disable(); > sco_conn_lock(conn); > sk = conn->sk; > sco_conn_unlock(conn); > + local_bh_enable(); > > if (!sk) > goto drop; > @@ -420,18 +430,25 @@ static void __sco_sock_close(struct sock *sk) > if (sco_pi(sk)->conn->hcon) { > sk->sk_state = BT_DISCONN; > sco_sock_set_timer(sk, SCO_DISCONN_TIMEOUT); > + local_bh_disable(); > sco_conn_lock(sco_pi(sk)->conn); > hci_conn_drop(sco_pi(sk)->conn->hcon); > sco_pi(sk)->conn->hcon = NULL; > sco_conn_unlock(sco_pi(sk)->conn); > - } else > + local_bh_enable(); > + } else { > + local_bh_disable(); > sco_chan_del(sk, ECONNRESET); > + local_bh_enable(); > + } > break; > > case BT_CONNECT2: > case BT_CONNECT: > case BT_DISCONN: > + local_bh_disable(); > sco_chan_del(sk, ECONNRESET); > + local_bh_enable(); > break; > > default: > @@ -1084,21 +1101,26 @@ static void sco_conn_ready(struct sco_conn *conn) > > if (sk) { > sco_sock_clear_timer(sk); > + local_bh_disable(); > bh_lock_sock(sk); > sk->sk_state = BT_CONNECTED; > sk->sk_state_change(sk); > bh_unlock_sock(sk); > + local_bh_enable(); > } else { > + local_bh_disable(); > sco_conn_lock(conn); > > if (!conn->hcon) { > sco_conn_unlock(conn); > + local_bh_enable(); > return; > } > > parent = sco_get_sock_listen(&conn->hcon->src); > if (!parent) { > sco_conn_unlock(conn); > + local_bh_enable(); > return; > } > > @@ -1109,6 +1131,7 @@ static void sco_conn_ready(struct sco_conn *conn) > if (!sk) { > bh_unlock_sock(parent); > sco_conn_unlock(conn); > + local_bh_enable(); > return; > } > > @@ -1131,6 +1154,7 @@ static void sco_conn_ready(struct sco_conn *conn) > bh_unlock_sock(parent); > > sco_conn_unlock(conn); > + local_bh_enable(); > } > } > > -- > 2.25.1 >
On 15/7/21 3:12 am, Luiz Augusto von Dentz wrote: > Hi Desmond, > > On Tue, Jul 13, 2021 at 9:29 AM Desmond Cheong Zhi Xi > <desmondcheongzx@gmail.com> wrote: >> >> Syzbot reported an inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} lock >> usage in sco_conn_del and sco_sock_timeout that could lead to >> deadlocks. >> >> This inconsistent lock state can also happen in sco_conn_ready, >> rfcomm_connect_ind, and bt_accept_enqueue. >> >> The issue is that these functions take a spin lock on the socket with >> interrupts enabled, but sco_sock_timeout takes the lock in an IRQ >> context. This could lead to deadlocks: >> >> CPU0 >> ---- >> lock(slock-AF_BLUETOOTH-BTPROTO_SCO); >> <Interrupt> >> lock(slock-AF_BLUETOOTH-BTPROTO_SCO); >> >> *** DEADLOCK *** >> >> We fix this by ensuring that local bh is disabled before calling >> bh_lock_sock. >> >> After doing this, we additionally need to protect sco_conn_lock by >> disabling local bh. >> >> This is necessary because sco_conn_del makes a call to sco_chan_del >> while holding on to the sock lock, and sco_chan_del itself makes a >> call to sco_conn_lock. If sco_conn_lock is held elsewhere with >> interrupts enabled, there could still be a >> slock-AF_BLUETOOTH-BTPROTO_SCO --> &conn->lock#2 lock inversion as >> follows: >> >> CPU0 CPU1 >> ---- ---- >> lock(&conn->lock#2); >> local_irq_disable(); >> lock(slock-AF_BLUETOOTH-BTPROTO_SCO); >> lock(&conn->lock#2); >> <Interrupt> >> lock(slock-AF_BLUETOOTH-BTPROTO_SCO); >> >> *** DEADLOCK *** >> >> As sco_conn_del now disables local bh before calling sco_chan_del, >> instead of disabling local bh for the calls to sco_conn_lock in >> sco_chan_del, we instead wrap other calls to sco_chan_del with >> local_bh_disable/enable. >> >> Reported-by: syzbot+2f6d7c28bb4bf7e82060@syzkaller.appspotmail.com >> Tested-by: syzbot+2f6d7c28bb4bf7e82060@syzkaller.appspotmail.com >> Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> >> --- >> >> Hi, >> >> The previous version of this patch was a bit of a mess, so I made the >> following changes. >> >> v1 -> v2: >> - Instead of pulling out the clean-up code out from sco_chan_del and >> using it directly in sco_conn_del, disable local irqs for relevant >> sections. >> - Disable local irqs more thoroughly for instances of >> bh_lock_sock/bh_lock_sock_nested in the bluetooth subsystem. >> Specifically, the calls in af_bluetooth.c and rfcomm/sock.c are now made >> with local irqs disabled as well. >> >> Best wishes, >> Desmond >> >> net/bluetooth/rfcomm/sock.c | 2 ++ >> net/bluetooth/sco.c | 26 +++++++++++++++++++++++++- >> 2 files changed, 27 insertions(+), 1 deletion(-) >> >> diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c >> index ae6f80730561..d8734abb2df4 100644 >> --- a/net/bluetooth/rfcomm/sock.c >> +++ b/net/bluetooth/rfcomm/sock.c >> @@ -974,6 +974,7 @@ int rfcomm_connect_ind(struct rfcomm_session *s, u8 channel, struct rfcomm_dlc * >> if (!parent) >> return 0; >> >> + local_bh_disable(); >> bh_lock_sock(parent); >> >> /* Check for backlog size */ >> @@ -1002,6 +1003,7 @@ int rfcomm_connect_ind(struct rfcomm_session *s, u8 channel, struct rfcomm_dlc * >> >> done: >> bh_unlock_sock(parent); >> + local_bh_enable(); > > Looks like you are touching RFCOMM as well, perhaps you should have it > split, also how about other sockets like L2CAP and HCI are they > affected? There seems to be a lot of problem with the likes of > bh_lock_sock I wonder if going with local_bh_disable is overall a > better way to handle. > Thanks for the feedback, Luiz. I'll separate the SCO and RFCOMM code changes. I believe other sockets should be fine. From what I see, they use lock_sock, which acquires the spin lock via spin_lock_bh under the hood. So only code that uses bh_lock_sock/bh_lock_sock_nested are affected. Also I'm not sure what you meant by going with local_bh_disable? I'm probably missing context about Bluetooth protocols, but I think the spin locks still have their place to protect concurrent accesses and to make it clear about what's being protected. >> if (test_bit(BT_SK_DEFER_SETUP, &bt_sk(parent)->flags)) >> parent->sk_state_change(parent); >> diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c >> index 3bd41563f118..2548b8f81473 100644 >> --- a/net/bluetooth/sco.c >> +++ b/net/bluetooth/sco.c >> @@ -167,16 +167,22 @@ static void sco_conn_del(struct hci_conn *hcon, int err) >> BT_DBG("hcon %p conn %p, err %d", hcon, conn, err); >> >> /* Kill socket */ >> + local_bh_disable(); >> sco_conn_lock(conn); >> sk = conn->sk; >> sco_conn_unlock(conn); >> + local_bh_enable(); >> >> if (sk) { >> sock_hold(sk); >> + >> + local_bh_disable(); >> bh_lock_sock(sk); >> sco_sock_clear_timer(sk); >> sco_chan_del(sk, err); >> bh_unlock_sock(sk); >> + local_bh_enable(); >> + >> sco_sock_kill(sk); >> sock_put(sk); >> } >> @@ -202,6 +208,7 @@ static int sco_chan_add(struct sco_conn *conn, struct sock *sk, >> { >> int err = 0; >> >> + local_bh_disable(); >> sco_conn_lock(conn); >> if (conn->sk) >> err = -EBUSY; >> @@ -209,6 +216,7 @@ static int sco_chan_add(struct sco_conn *conn, struct sock *sk, >> __sco_chan_add(conn, sk, parent); >> >> sco_conn_unlock(conn); >> + local_bh_enable(); >> return err; >> } >> >> @@ -303,9 +311,11 @@ static void sco_recv_frame(struct sco_conn *conn, struct sk_buff *skb) >> { >> struct sock *sk; >> >> + local_bh_disable(); >> sco_conn_lock(conn); >> sk = conn->sk; >> sco_conn_unlock(conn); >> + local_bh_enable(); >> >> if (!sk) >> goto drop; >> @@ -420,18 +430,25 @@ static void __sco_sock_close(struct sock *sk) >> if (sco_pi(sk)->conn->hcon) { >> sk->sk_state = BT_DISCONN; >> sco_sock_set_timer(sk, SCO_DISCONN_TIMEOUT); >> + local_bh_disable(); >> sco_conn_lock(sco_pi(sk)->conn); >> hci_conn_drop(sco_pi(sk)->conn->hcon); >> sco_pi(sk)->conn->hcon = NULL; >> sco_conn_unlock(sco_pi(sk)->conn); >> - } else >> + local_bh_enable(); >> + } else { >> + local_bh_disable(); >> sco_chan_del(sk, ECONNRESET); >> + local_bh_enable(); >> + } >> break; >> >> case BT_CONNECT2: >> case BT_CONNECT: >> case BT_DISCONN: >> + local_bh_disable(); >> sco_chan_del(sk, ECONNRESET); >> + local_bh_enable(); >> break; >> >> default: >> @@ -1084,21 +1101,26 @@ static void sco_conn_ready(struct sco_conn *conn) >> >> if (sk) { >> sco_sock_clear_timer(sk); >> + local_bh_disable(); >> bh_lock_sock(sk); >> sk->sk_state = BT_CONNECTED; >> sk->sk_state_change(sk); >> bh_unlock_sock(sk); >> + local_bh_enable(); >> } else { >> + local_bh_disable(); >> sco_conn_lock(conn); >> >> if (!conn->hcon) { >> sco_conn_unlock(conn); >> + local_bh_enable(); >> return; >> } >> >> parent = sco_get_sock_listen(&conn->hcon->src); >> if (!parent) { >> sco_conn_unlock(conn); >> + local_bh_enable(); >> return; >> } >> >> @@ -1109,6 +1131,7 @@ static void sco_conn_ready(struct sco_conn *conn) >> if (!sk) { >> bh_unlock_sock(parent); >> sco_conn_unlock(conn); >> + local_bh_enable(); >> return; >> } >> >> @@ -1131,6 +1154,7 @@ static void sco_conn_ready(struct sco_conn *conn) >> bh_unlock_sock(parent); >> >> sco_conn_unlock(conn); >> + local_bh_enable(); >> } >> } >> >> -- >> 2.25.1 >> > >
diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c index ae6f80730561..d8734abb2df4 100644 --- a/net/bluetooth/rfcomm/sock.c +++ b/net/bluetooth/rfcomm/sock.c @@ -974,6 +974,7 @@ int rfcomm_connect_ind(struct rfcomm_session *s, u8 channel, struct rfcomm_dlc * if (!parent) return 0; + local_bh_disable(); bh_lock_sock(parent); /* Check for backlog size */ @@ -1002,6 +1003,7 @@ int rfcomm_connect_ind(struct rfcomm_session *s, u8 channel, struct rfcomm_dlc * done: bh_unlock_sock(parent); + local_bh_enable(); if (test_bit(BT_SK_DEFER_SETUP, &bt_sk(parent)->flags)) parent->sk_state_change(parent); diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c index 3bd41563f118..2548b8f81473 100644 --- a/net/bluetooth/sco.c +++ b/net/bluetooth/sco.c @@ -167,16 +167,22 @@ static void sco_conn_del(struct hci_conn *hcon, int err) BT_DBG("hcon %p conn %p, err %d", hcon, conn, err); /* Kill socket */ + local_bh_disable(); sco_conn_lock(conn); sk = conn->sk; sco_conn_unlock(conn); + local_bh_enable(); if (sk) { sock_hold(sk); + + local_bh_disable(); bh_lock_sock(sk); sco_sock_clear_timer(sk); sco_chan_del(sk, err); bh_unlock_sock(sk); + local_bh_enable(); + sco_sock_kill(sk); sock_put(sk); } @@ -202,6 +208,7 @@ static int sco_chan_add(struct sco_conn *conn, struct sock *sk, { int err = 0; + local_bh_disable(); sco_conn_lock(conn); if (conn->sk) err = -EBUSY; @@ -209,6 +216,7 @@ static int sco_chan_add(struct sco_conn *conn, struct sock *sk, __sco_chan_add(conn, sk, parent); sco_conn_unlock(conn); + local_bh_enable(); return err; } @@ -303,9 +311,11 @@ static void sco_recv_frame(struct sco_conn *conn, struct sk_buff *skb) { struct sock *sk; + local_bh_disable(); sco_conn_lock(conn); sk = conn->sk; sco_conn_unlock(conn); + local_bh_enable(); if (!sk) goto drop; @@ -420,18 +430,25 @@ static void __sco_sock_close(struct sock *sk) if (sco_pi(sk)->conn->hcon) { sk->sk_state = BT_DISCONN; sco_sock_set_timer(sk, SCO_DISCONN_TIMEOUT); + local_bh_disable(); sco_conn_lock(sco_pi(sk)->conn); hci_conn_drop(sco_pi(sk)->conn->hcon); sco_pi(sk)->conn->hcon = NULL; sco_conn_unlock(sco_pi(sk)->conn); - } else + local_bh_enable(); + } else { + local_bh_disable(); sco_chan_del(sk, ECONNRESET); + local_bh_enable(); + } break; case BT_CONNECT2: case BT_CONNECT: case BT_DISCONN: + local_bh_disable(); sco_chan_del(sk, ECONNRESET); + local_bh_enable(); break; default: @@ -1084,21 +1101,26 @@ static void sco_conn_ready(struct sco_conn *conn) if (sk) { sco_sock_clear_timer(sk); + local_bh_disable(); bh_lock_sock(sk); sk->sk_state = BT_CONNECTED; sk->sk_state_change(sk); bh_unlock_sock(sk); + local_bh_enable(); } else { + local_bh_disable(); sco_conn_lock(conn); if (!conn->hcon) { sco_conn_unlock(conn); + local_bh_enable(); return; } parent = sco_get_sock_listen(&conn->hcon->src); if (!parent) { sco_conn_unlock(conn); + local_bh_enable(); return; } @@ -1109,6 +1131,7 @@ static void sco_conn_ready(struct sco_conn *conn) if (!sk) { bh_unlock_sock(parent); sco_conn_unlock(conn); + local_bh_enable(); return; } @@ -1131,6 +1154,7 @@ static void sco_conn_ready(struct sco_conn *conn) bh_unlock_sock(parent); sco_conn_unlock(conn); + local_bh_enable(); } }
Syzbot reported an inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} lock usage in sco_conn_del and sco_sock_timeout that could lead to deadlocks. This inconsistent lock state can also happen in sco_conn_ready, rfcomm_connect_ind, and bt_accept_enqueue. The issue is that these functions take a spin lock on the socket with interrupts enabled, but sco_sock_timeout takes the lock in an IRQ context. This could lead to deadlocks: CPU0 ---- lock(slock-AF_BLUETOOTH-BTPROTO_SCO); <Interrupt> lock(slock-AF_BLUETOOTH-BTPROTO_SCO); *** DEADLOCK *** We fix this by ensuring that local bh is disabled before calling bh_lock_sock. After doing this, we additionally need to protect sco_conn_lock by disabling local bh. This is necessary because sco_conn_del makes a call to sco_chan_del while holding on to the sock lock, and sco_chan_del itself makes a call to sco_conn_lock. If sco_conn_lock is held elsewhere with interrupts enabled, there could still be a slock-AF_BLUETOOTH-BTPROTO_SCO --> &conn->lock#2 lock inversion as follows: CPU0 CPU1 ---- ---- lock(&conn->lock#2); local_irq_disable(); lock(slock-AF_BLUETOOTH-BTPROTO_SCO); lock(&conn->lock#2); <Interrupt> lock(slock-AF_BLUETOOTH-BTPROTO_SCO); *** DEADLOCK *** As sco_conn_del now disables local bh before calling sco_chan_del, instead of disabling local bh for the calls to sco_conn_lock in sco_chan_del, we instead wrap other calls to sco_chan_del with local_bh_disable/enable. Reported-by: syzbot+2f6d7c28bb4bf7e82060@syzkaller.appspotmail.com Tested-by: syzbot+2f6d7c28bb4bf7e82060@syzkaller.appspotmail.com Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> --- Hi, The previous version of this patch was a bit of a mess, so I made the following changes. v1 -> v2: - Instead of pulling out the clean-up code out from sco_chan_del and using it directly in sco_conn_del, disable local irqs for relevant sections. - Disable local irqs more thoroughly for instances of bh_lock_sock/bh_lock_sock_nested in the bluetooth subsystem. Specifically, the calls in af_bluetooth.c and rfcomm/sock.c are now made with local irqs disabled as well. Best wishes, Desmond net/bluetooth/rfcomm/sock.c | 2 ++ net/bluetooth/sco.c | 26 +++++++++++++++++++++++++- 2 files changed, 27 insertions(+), 1 deletion(-)