[3.11.y.z extended stable] Patch "inet: frag: make sure forced eviction removes all frags" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    inet: frag: make sure forced eviction removes all frags

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 3ea18c28f325ce5a7586aeccf795cf72a65ebad8 Mon Sep 17 00:00:00 2001
From: Florian Westphal <fw at strlen.de>
Date: Thu, 6 Mar 2014 18:06:41 +0100
Subject: inet: frag: make sure forced eviction removes all frags

commit e588e2f286ed7da011ed357c24c5b9a554e26595 upstream.

Quoting Alexander Aring:
  While fragmentation and unloading of 6lowpan module I got this kernel Oops
  after few seconds:

  BUG: unable to handle kernel paging request at f88bbc30
  [..]
  Modules linked in: ipv6 [last unloaded: 6lowpan]
  Call Trace:
   [<c012af4c>] ? call_timer_fn+0x54/0xb3
   [<c012aef8>] ? process_timeout+0xa/0xa
   [<c012b66b>] run_timer_softirq+0x140/0x15f

Problem is that incomplete frags are still around after unload; when
their frag expire timer fires, we get crash.

When a netns is removed (also done when unloading module), inet_frag
calls the evictor with 'force' argument to purge remaining frags.

The evictor loop terminates when accounted memory ('work') drops to 0
or the lru-list becomes empty.  However, the mem accounting is done
via percpu counters and may not be accurate, i.e. loop may terminate
prematurely.

Alter evictor to only stop once the lru list is empty when force is
requested.

Reported-by: Phoebe Buckheister <phoebe.buckheister at itwm.fraunhofer.de>
Reported-by: Alexander Aring <alex.aring at gmail.com>
Tested-by: Alexander Aring <alex.aring at gmail.com>
Signed-off-by: Florian Westphal <fw at strlen.de>
Acked-by: Eric Dumazet <edumazet at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/ipv4/inet_fragment.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c
index e15fb7b..12b80fb 100644
--- a/net/ipv4/inet_fragment.c
+++ b/net/ipv4/inet_fragment.c
@@ -211,7 +211,7 @@ int inet_frag_evictor(struct netns_frags *nf, struct inet_frags *f, bool force)
 	}

 	work = frag_mem_limit(nf) - nf->low_thresh;
-	while (work > 0) {
+	while (work > 0 || force) {
 		spin_lock(&nf->lru_lock);

 		if (list_empty(&nf->lru_list)) {
--
1.9.1