Hi All,
I have done second experimental version of the patch.
Main difference is that when sk is owned by user I do not run
"l2cap_chan_del" example below:
+ /* don't delete l2cap channel if sk is owned by user */
+ if (sock_owned_by_user(sk)) {
+ sk->sk_state = BT_DISCONN;
+ l2cap_sock_clear_timer(sk);
+ l2cap_sock_set_timer(sk, HZ);
+ bh_unlock_sock(sk);
+ return 0;
+ }
I start timer which will run this function. I do also the same check
in timer context.
+ if (sock_owned_by_user(sk)) {
+ /* sk is owned by user. Try again later */
+ l2cap_sock_set_timer(sk, HZ * 2);
+ bh_unlock_sock(sk);
+ sock_put(sk);
+ return;
+ }
Please give me your comments.
Regards,
Andrei
From e0ab5b30d3c507224043f065c1c227f55ae29814 Mon Sep 17 00:00:00 2001
From: Andrei Emeltchenko <andrei.emeltchenko@xxxxxxxxx>
Date: Mon, 17 May 2010 12:10:46 +0300
Subject: [PATCHv2 1/2] Bluetooth: Check sk is not owned before freeing l2cap_conn
Check that socket sk is not locked in user process before removing
l2cap connection handler.
krfcommd kernel thread may be preempted with l2cap tasklet which remove
l2cap_conn structure. If krfcommd is in process of sending of RFCOMM reply
(like "RFCOMM UA" reply to "RFCOMM DISC") then kernel crash happens.
...
[ 694.175933] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[ 694.184936] pgd = c0004000
[ 694.187683] [00000000] *pgd=00000000
[ 694.191711] Internal error: Oops: 5 [#1] PREEMPT
[ 694.196350] last sysfs file: /sys/devices/platform/hci_h4p/firmware/hci_h4p/loading
[ 694.260375] CPU: 0 Not tainted (2.6.32.10 #1)
[ 694.265106] PC is at l2cap_sock_sendmsg+0x43c/0x73c [l2cap]
[ 694.270721] LR is at 0xd7017303
...
[ 694.525085] Backtrace:
[ 694.527587] [<bf266be0>] (l2cap_sock_sendmsg+0x0/0x73c [l2cap]) from [<c02f2cc8>] (sock_sendmsg+0xb8/0xd8)
[ 694.537292] [<c02f2c10>] (sock_sendmsg+0x0/0xd8) from [<c02f3044>] (kernel_sendmsg+0x48/0x80)
...
Modified version after comments of Gustavo F. Padovan <gustavo@xxxxxxxxxxx>
Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@xxxxxxxxx>
---
net/bluetooth/l2cap.c | 25 +++++++++++++++++++++++++
1 files changed, 25 insertions(+), 0 deletions(-)
diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index bb00015..11060d6 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -2927,6 +2927,13 @@ static inline int l2cap_connect_rsp(struct l2cap_conn *conn, struct l2cap_cmd_hd
break;
default:
+ /* don't delete l2cap channel if sk is owned by user */
+ if (sock_owned_by_user(sk)) {
+ sk->sk_state = BT_DISCONN;
+ l2cap_sock_clear_timer(sk);
+ l2cap_sock_set_timer(sk, HZ);
+ break;
+ }
l2cap_chan_del(sk, ECONNREFUSED);
break;
}
@@ -3135,6 +3142,15 @@ static inline int l2cap_disconnect_req(struct l2cap_conn *conn, struct l2cap_cmd
del_timer(&l2cap_pi(sk)->ack_timer);
}
+ /* don't delete l2cap channel if sk is owned by user */
+ if (sock_owned_by_user(sk)) {
+ sk->sk_state = BT_DISCONN;
+ l2cap_sock_clear_timer(sk);
+ l2cap_sock_set_timer(sk, HZ);
+ bh_unlock_sock(sk);
+ return 0;
+ }
+
l2cap_chan_del(sk, ECONNRESET);
bh_unlock_sock(sk);
@@ -3167,6 +3183,15 @@ static inline int l2cap_disconnect_rsp(struct l2cap_conn *conn, struct l2cap_cmd
del_timer(&l2cap_pi(sk)->ack_timer);
}
+ /* don't delete l2cap channel if sk is owned by user */
+ if (sock_owned_by_user(sk)) {
+ sk->sk_state = BT_DISCONN;
+ l2cap_sock_clear_timer(sk);
+ l2cap_sock_set_timer(sk, HZ);
+ bh_unlock_sock(sk);
+ return 0;
+ }
+
l2cap_chan_del(sk, 0);
bh_unlock_sock(sk);
--
1.7.0.4
From 5adfee7a73883180e6b606cc46b792fbefbb6758 Mon Sep 17 00:00:00 2001
From: Andrei Emeltchenko <andrei.emeltchenko@xxxxxxxxx>
Date: Thu, 20 May 2010 16:52:19 +0300
Subject: [PATCHv2 2/2] Bluetooth: timer check sk is not owned before freeing
In timer context we might delete l2cap channel used by krfcommd.
The check makes sure that sk is not owned.
Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@xxxxxxxxx>
---
net/bluetooth/l2cap.c | 8 ++++++++
1 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index 11060d6..19d2fc1 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -93,6 +93,14 @@ static void l2cap_sock_timeout(unsigned long arg)
bh_lock_sock(sk);
+ if (sock_owned_by_user(sk)) {
+ /* sk is owned by user. Try again later */
+ l2cap_sock_set_timer(sk, HZ * 2);
+ bh_unlock_sock(sk);
+ sock_put(sk);
+ return;
+ }
+
if (sk->sk_state == BT_CONNECTED || sk->sk_state == BT_CONFIG)
reason = ECONNREFUSED;
else if (sk->sk_state == BT_CONNECT &&
--
1.7.0.4
