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[ATM]: fix possible recursive locking in skb_migrate() 

ok this is a real potential deadlock in a way, it takes two locks of 2
skbuffs without doing any kind of lock ordering; I think the following
patch should fix it. Just sort the lock taking order by address of the
skb.. it's not pretty but it's the best this can do in a minimally
invasive way.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Chas Williams <chas@cmf.nrl.navy.mil>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Arjan van de Ven 2006-07-08 13:30:52 -07:00 committed by David S. Miller
parent 00181fc946
commit 1252ecf63f
1 changed files with 11 additions and 6 deletions
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17
net/atm/ipcommon.c
View File

@ -25,22 +25,27 @@
/*
* skb_migrate appends the list at "from" to "to", emptying "from" in the
* process. skb_migrate is atomic with respect to all other skb operations on
* "from" and "to". Note that it locks both lists at the same time, so beware
* of potential deadlocks.
* "from" and "to". Note that it locks both lists at the same time, so to deal
* with the lock ordering, the locks are taken in address order.
*
* This function should live in skbuff.c or skbuff.h.
*/
void skb_migrate(struct sk_buff_head *from,struct sk_buff_head *to)
void skb_migrate(struct sk_buff_head *from, struct sk_buff_head *to)
{
unsigned long flags;
struct sk_buff *skb_from = (struct sk_buff *) from;
struct sk_buff *skb_to = (struct sk_buff *) to;
struct sk_buff *prev;
spin_lock_irqsave(&from->lock,flags);
spin_lock(&to->lock);
if ((unsigned long) from < (unsigned long) to) {
spin_lock_irqsave(&from->lock, flags);
spin_lock_nested(&to->lock, SINGLE_DEPTH_NESTING);
} else {
spin_lock_irqsave(&to->lock, flags);
spin_lock_nested(&from->lock, SINGLE_DEPTH_NESTING);
}
prev = from->prev;
from->next->prev = to->prev;
prev->next = skb_to;
@ -51,7 +56,7 @@ void skb_migrate(struct sk_buff_head *from,struct sk_buff_head *to)
from->prev = skb_from;
from->next = skb_from;
from->qlen = 0;
spin_unlock_irqrestore(&from->lock,flags);
spin_unlock_irqrestore(&from->lock, flags);
}