linux-kernel - [PATCH 4.2 095/110] netfilter: ipset: Fix sleeping memory allocation in atomic context

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Message-Id: <20151106191708.937933695@linuxfoundation.org>
Date:	Fri,  6 Nov 2015 11:19:42 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Nikolay Borisov <kernel@...p.com>,
	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
	Pablo Neira Ayuso <pablo@...filter.org>
Subject: [PATCH 4.2 095/110] netfilter: ipset: Fix sleeping memory allocation in atomic context

4.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nikolay Borisov <kernel@...p.com>

commit 00db674bedd68ff8b5afae9030ff5e04d45d1b4a upstream.

Commit 00590fdd5be0 introduced RCU locking in list type and in
doing so introduced a memory allocation in list_set_add, which
is done in an atomic context, due to the fact that ipset rcu
list modifications are serialised with a spin lock. The reason
why we can't use a mutex is that in addition to modifying the
list with ipset commands, it's also being modified when a
particular ipset rule timeout expires aka garbage collection.
This gc is triggered from set_cleanup_entries, which in turn
is invoked from a timer thus requiring the lock to be bh-safe.

Concretely the following call chain can lead to "sleeping function
called in atomic context" splat:
call_ad -> list_set_uadt -> list_set_uadd -> kzalloc(, GFP_KERNEL).
And since GFP_KERNEL allows initiating direct reclaim thus
potentially sleeping in the allocation path.

To fix the issue change the allocation type to GFP_ATOMIC, to
correctly reflect that it is occuring in an atomic context.

Fixes: 00590fdd5be0 ("netfilter: ipset: Introduce RCU locking in list type")
Signed-off-by: Nikolay Borisov <kernel@...p.com>
Acked-by: Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/netfilter/ipset/ip_set_list_set.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/netfilter/ipset/ip_set_list_set.c
+++ b/net/netfilter/ipset/ip_set_list_set.c
@@ -297,7 +297,7 @@ list_set_uadd(struct ip_set *set, void *
 	      ip_set_timeout_expired(ext_timeout(n, set))))
 		n =  NULL;

-	e = kzalloc(set->dsize, GFP_KERNEL);
+	e = kzalloc(set->dsize, GFP_ATOMIC);
 	if (!e)
 		return -ENOMEM;
 	e->id = d->id;

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