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authorPablo Neira <pablo@netfilter.org>2013-06-28 03:04:23 +0200
committerDavid S. Miller <davem@davemloft.net>2013-06-27 22:44:16 -0700
commit3a36515f729458c8efa0c124c7262d5843ad5c37 (patch)
tree75924228bbebccdbbbbe1c8cca9b65d121843a0a /net/netlink
parent5e6700b3bf98fe98d630bf9c939ad4c85ce95592 (diff)
downloadlinux-3a36515f729458c8efa0c124c7262d5843ad5c37.tar.gz
netlink: fix splat in skb_clone with large messages
Since (c05cdb1 netlink: allow large data transfers from user-space), netlink splats if it invokes skb_clone on large netlink skbs since: * skb_shared_info was not correctly initialized. * skb->destructor is not set in the cloned skb. This was spotted by trinity: [ 894.990671] BUG: unable to handle kernel paging request at ffffc9000047b001 [ 894.991034] IP: [<ffffffff81a212c4>] skb_clone+0x24/0xc0 [...] [ 894.991034] Call Trace: [ 894.991034] [<ffffffff81ad299a>] nl_fib_input+0x6a/0x240 [ 894.991034] [<ffffffff81c3b7e6>] ? _raw_read_unlock+0x26/0x40 [ 894.991034] [<ffffffff81a5f189>] netlink_unicast+0x169/0x1e0 [ 894.991034] [<ffffffff81a601e1>] netlink_sendmsg+0x251/0x3d0 Fix it by: 1) introducing a new netlink_skb_clone function that is used in nl_fib_input, that sets our special skb->destructor in the cloned skb. Moreover, handle the release of the large cloned skb head area in the destructor path. 2) not allowing large skbuffs in the netlink broadcast path. I cannot find any reasonable use of the large data transfer using netlink in that path, moreover this helps to skip extra skb_clone handling. I found two more netlink clients that are cloning the skbs, but they are not in the sendmsg path. Therefore, the sole client cloning that I found seems to be the fib frontend. Thanks to Eric Dumazet for helping to address this issue. Reported-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/netlink')
-rw-r--r--net/netlink/af_netlink.c35
1 files changed, 18 insertions, 17 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 6967fbcca6c..0c61b59175d 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -849,7 +849,10 @@ static void netlink_skb_destructor(struct sk_buff *skb)
}
#endif
if (is_vmalloc_addr(skb->head)) {
- vfree(skb->head);
+ if (!skb->cloned ||
+ !atomic_dec_return(&(skb_shinfo(skb)->dataref)))
+ vfree(skb->head);
+
skb->head = NULL;
}
if (skb->sk != NULL)
@@ -1532,33 +1535,31 @@ struct sock *netlink_getsockbyfilp(struct file *filp)
return sock;
}
-static struct sk_buff *netlink_alloc_large_skb(unsigned int size)
+static struct sk_buff *netlink_alloc_large_skb(unsigned int size,
+ int broadcast)
{
struct sk_buff *skb;
void *data;
- if (size <= NLMSG_GOODSIZE)
+ if (size <= NLMSG_GOODSIZE || broadcast)
return alloc_skb(size, GFP_KERNEL);
- skb = alloc_skb_head(GFP_KERNEL);
- if (skb == NULL)
- return NULL;
+ size = SKB_DATA_ALIGN(size) +
+ SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
data = vmalloc(size);
if (data == NULL)
- goto err;
+ return NULL;
- skb->head = data;
- skb->data = data;
- skb_reset_tail_pointer(skb);
- skb->end = skb->tail + size;
- skb->len = 0;
- skb->destructor = netlink_skb_destructor;
+ skb = build_skb(data, size);
+ if (skb == NULL)
+ vfree(data);
+ else {
+ skb->head_frag = 0;
+ skb->destructor = netlink_skb_destructor;
+ }
return skb;
-err:
- kfree_skb(skb);
- return NULL;
}
/*
@@ -2244,7 +2245,7 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
if (len > sk->sk_sndbuf - 32)
goto out;
err = -ENOBUFS;
- skb = netlink_alloc_large_skb(len);
+ skb = netlink_alloc_large_skb(len, dst_group);
if (skb == NULL)
goto out;