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| author | Pablo Neira <pablo@netfilter.org> | 2013-06-28 03:04:23 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2013-06-27 22:44:16 -0700 |
| commit | 3a36515f729458c8efa0c124c7262d5843ad5c37 (patch) | |
| tree | 75924228bbebccdbbbbe1c8cca9b65d121843a0a /include/linux/netlink.h | |
| parent | 5e6700b3bf98fe98d630bf9c939ad4c85ce95592 (diff) | |
| download | lwn-3a36515f729458c8efa0c124c7262d5843ad5c37.tar.gz lwn-3a36515f729458c8efa0c124c7262d5843ad5c37.zip | |
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 'include/linux/netlink.h')
| -rw-r--r-- | include/linux/netlink.h | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/include/linux/netlink.h b/include/linux/netlink.h index 86fde81ac2e6..7a6c396a263b 100644 --- a/include/linux/netlink.h +++ b/include/linux/netlink.h @@ -85,6 +85,22 @@ int netlink_attachskb(struct sock *sk, struct sk_buff *skb, void netlink_detachskb(struct sock *sk, struct sk_buff *skb); int netlink_sendskb(struct sock *sk, struct sk_buff *skb); +static inline struct sk_buff * +netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask) +{ + struct sk_buff *nskb; + + nskb = skb_clone(skb, gfp_mask); + if (!nskb) + return NULL; + + /* This is a large skb, set destructor callback to release head */ + if (is_vmalloc_addr(skb->head)) + nskb->destructor = skb->destructor; + + return nskb; +} + /* * skb should fit one page. This choice is good for headerless malloc. * But we should limit to 8K so that userspace does not have to |