On Fri, Dec 14, 2007 at 11:29:28PM +0100, Bernard Pidoux wrote:
> Hi,
>
> This patch cancels a circular locking conflict that appeared with a timeout
> of an AX25 connection.
>
> signed off by Jarek Poplawski
One spurious space less here, and maybe a few more words to the changelog.
Regards,
Jarek P.
---------------->
Subject: [PATCH] [NET] AX25: locking dependencies fix in ax25_disconnect
Bernard Pidoux reported these lockdep warnings:
[ INFO: possible irq lock inversion dependency detected ]
2.6.23.1 #1
---------------------------------------------------------
fpac/4933 just changed the state of lock:
(slock-AF_AX25){--..}, at: [<d8be3312>] ax25_disconnect+0x46/0xaf
[ax25]
but this lock was taken by another, soft-irq-safe lock in the past:
(ax25_list_lock){-+..}
and interrupts could create inverse lock ordering between them.
[...]
[ INFO: inconsistent lock state ]
2.6.23.1 #1
---------------------------------
inconsistent {in-softirq-W} -> {softirq-on-W} usage.
ax25_call/4005 [HC0[0]:SC0[0]:HE1:SE1] takes:
(slock-AF_AX25){-+..}, at: [<d8b79312>] ax25_disconnect+0x46/0xaf [ax25]
[...]
This means slock-AF_AX25 could be taken both from softirq and process
context with softirqs enabled, so it's endangered itself, but also makes
ax25_list_lock vulnerable. It was not 100% verified if the real lockup
can happen, but this fix isn't very costly and looks safe anyway.
(It was tested by Bernard with 2.6.23.9 and 2.6.24-rc5 kernels.)
Reported_by: Bernard Pidoux <[EMAIL PROTECTED]>
Tested_by: Bernard Pidoux <[EMAIL PROTECTED]>
Signed-off-by: Jarek Poplawski <[EMAIL PROTECTED]>
---
diff -Nurp linux-2.6.24-rc2-/net/ax25/ax25_subr.c
linux-2.6.24-rc2+/net/ax25/ax25_subr.c
--- linux-2.6.24-rc2-/net/ax25/ax25_subr.c 2007-10-09 22:31:38.000000000
+0200
+++ linux-2.6.24-rc2+/net/ax25/ax25_subr.c 2007-11-28 11:51:12.000000000
+0100
@@ -279,6 +279,7 @@ void ax25_disconnect(ax25_cb *ax25, int
ax25_link_failed(ax25, reason);
if (ax25->sk != NULL) {
+ local_bh_disable();
bh_lock_sock(ax25->sk);
ax25->sk->sk_state = TCP_CLOSE;
ax25->sk->sk_err = reason;
@@ -288,5 +289,6 @@ void ax25_disconnect(ax25_cb *ax25, int
sock_set_flag(ax25->sk, SOCK_DEAD);
}
bh_unlock_sock(ax25->sk);
+ local_bh_enable();
}
}
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
