please consider for 2.6.18 -- thanks!
[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 <[EMAIL PROTECTED]>
Signed-off-by: Chas Williams <[EMAIL PROTECTED]>
---
commit c895a2f42057801ca096f5155e85bc2b2f381250
tree ee64100fdd0302fe5c12ce6c153eea8b94010f2b
parent 8bbf3465e23c41b92931e2d2172c184ccd1d2510
author chas williams <[EMAIL PROTECTED]> Fri, 07 Jul 2006 18:11:30 -0400
committer chas williams <[EMAIL PROTECTED]> Fri, 07 Jul 2006 18:11:30 -0400
net/atm/ipcommon.c | 17 +++++++++++------
1 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/net/atm/ipcommon.c b/net/atm/ipcommon.c
index 4b1faca..1d3de42 100644
--- a/net/atm/ipcommon.c
+++ b/net/atm/ipcommon.c
@@ -25,22 +25,27 @@ #endif
/*
* 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 *fr
from->prev = skb_from;
from->next = skb_from;
from->qlen = 0;
- spin_unlock_irqrestore(&from->lock,flags);
+ spin_unlock_irqrestore(&from->lock, flags);
}
-
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