netdev - Re: panic with 2.6.28 while doing "ip -6 route"

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Message-ID: <20090114053534.GA15267@gondor.apana.org.au>
Date:	Wed, 14 Jan 2009 16:35:34 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	"David S. Miller" <davem@...emloft.net>,
	Chris Caputo <ccaputo@....net>
Cc:	netdev@...r.kernel.org
Subject: Re: panic with 2.6.28 while doing "ip -6 route"

On Wed, Jan 14, 2009 at 02:30:11AM +0000, Chris Caputo wrote:
> On a 2.6.28 x86 system with a full IPv6 route table - 1,524 routes - I can 
> reproducibly panic the system with the following:
> 
>   ip -6 route | head
> 
> The above finishes and a command prompt is shown.  Then about half of the 
> time I get a panic:
> 
>  BUG: unable to handle kernel paging request at 01000014
>   [<c0432168>] ? inet6_rtm_delroute+0x0/0x22
>   [<c0432184>] ? inet6_rtm_delroute+0x1c/0x22
>   [<c03a0e4b>] ? rtnetlink_rcv_msg+0x188/0x1a2
>   [<c03a0cc3>] ? rtnetlink_rcv_msg+0x0/0x1a2
>   [<c03bdf1f>] ? netlink_rcv_skb+0x30/0x75
>   [<c03a0cbb>] ? rtnetlink_rcv+0x17/0x1f
>   [<c03bdd50>] ? netlink_unicast+0x1a8/0x209
>   [<c03be40d>] ? netlink_sendmsg+0x21a/0x227
>   [<c038f25f>] ? sock_sendmsg+0xca/0xe1
>   [<c0231271>] ? autoremove_wake_function+0x0/0x33
>   [<c02077f8>] ? nommu_map_single+0x0/0x41
>   [<c0398149>] ? dev_kfree_skb_any+0x23/0x2e
>   [<f807a73b>] ? e1000_unmap_and_free_tx_resource+0x5b/0x70 [e1000]
>   [<c02fbb92>] ? copy_from_user+0x2c/0x4f
>   [<c03953e1>] ? verify_iovec+0x40/0x73
>   [<c038f3c5>] ? sys_sendmsg+0x14f/0x1aa
>   [<c03900bb>] ? sys_socketcall+0x140/0x16d
>   [<c0202bf1>] ? sysenter_do_call+0x12/0x25
>  Code: 00 ff 48 0c 8b 81 dc 01 00 00 ff 40 14 39 53 18 75 07 c7 43 18 00 00 00 00 b8 d0 2d 5a c0 e8 a6 3f 04 00 8b 15 e4 2d 5a c0 eb 1f <80> 7a 14 02 75 16 39 72 10 75 11 8b 86 88 00 00 00 85 c0 89 42
>  EIP: [<c04345e1>] fib6_del+0xd9/0x395 SS:ESP 0068:f6457c10
>  Kernel panic - not syncing: Fatal exception in interrupt
>  Rebooting in 10 seconds..

I'm surprised that it's taken nearly 3 years for this bug to
show itself.  It even survived a move from route.c :)

ipv6: Fix fib6_dump_table walker leak

When a fib6 table dump is prematurely ended, we won't unlink
its walker from the list.  This causes all sorts of grief for
other users of the list later.

Reported-by: Chris Caputo <ccaputo@....net>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 29c7c99..52ee1dc 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -298,6 +298,10 @@ static void fib6_dump_end(struct netlink_callback *cb)
 	struct fib6_walker_t *w = (void*)cb->args[2];
 
 	if (w) {
+		if (cb->args[4]) {
+			cb->args[4] = 0;
+			fib6_walker_unlink(w);
+		}
 		cb->args[2] = 0;
 		kfree(w);
 	}
@@ -330,15 +334,12 @@ static int fib6_dump_table(struct fib6_table *table, struct sk_buff *skb,
 		read_lock_bh(&table->tb6_lock);
 		res = fib6_walk_continue(w);
 		read_unlock_bh(&table->tb6_lock);
-		if (res != 0) {
-			if (res < 0)
-				fib6_walker_unlink(w);
-			goto end;
+		if (res <= 0) {
+			fib6_walker_unlink(w);
+			cb->args[4] = 0;
 		}
-		fib6_walker_unlink(w);
-		cb->args[4] = 0;
 	}
-end:
+
 	return res;
 }

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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