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[AX25]: Locking dependencies fix in ax25_disconnect().

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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 <pidoux@ccr.jussieu.fr>
Tested_by: Bernard Pidoux <pidoux@ccr.jussieu.fr>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jarek Poplawski 2007-12-16 14:02:07 -08:00 committed by David S. Miller
parent 488faa2ae3
commit 215f7b08f2
1 changed files with 2 additions and 0 deletions
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2
net/ax25/ax25_subr.c
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@ -279,6 +279,7 @@ void ax25_disconnect(ax25_cb *ax25, int reason)
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 reason)
sock_set_flag(ax25->sk, SOCK_DEAD);
}
bh_unlock_sock(ax25->sk);
local_bh_enable();
}
}