netlink, mmap: transform mmap skb into full skb on taps
Ken-ichirou reported that running netlink in mmap mode for receive in
combination with nlmon will throw a NULL pointer dereference in
__kfree_skb() on nlmon_xmit(), in my case I can also trigger an "unable
to handle kernel paging request". The problem is the skb_clone() in
__netlink_deliver_tap_skb() for skbs that are mmaped.
I.e. the cloned skb doesn't have a destructor, whereas the mmap netlink
skb has it pointed to netlink_skb_destructor(), set in the handler
netlink_ring_setup_skb(). There, skb->head is being set to NULL, so
that in such cases, __kfree_skb() doesn't perform a skb_release_data()
via skb_release_all(), where skb->head is possibly being freed through
kfree(head) into slab allocator, although netlink mmap skb->head points
to the mmap buffer. Similarly, the same has to be done also for large
netlink skbs where the data area is vmalloced. Therefore, as discussed,
make a copy for these rather rare cases for now. This fixes the issue
on my and Ken-ichirou's test-cases.
Reference: http://thread.gmane.org/gmane.linux.network/371129
Fixes: bcbde0d449
("net: netlink: virtual tap device management")
Reported-by: Ken-ichirou MATSUZAWA <chamaken@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Ken-ichirou MATSUZAWA <chamaken@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
parent
64d1def7d3
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1853c94964
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@ -125,6 +125,24 @@ static inline u32 netlink_group_mask(u32 group)
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return group ? 1 << (group - 1) : 0;
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}
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static struct sk_buff *netlink_to_full_skb(const struct sk_buff *skb,
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gfp_t gfp_mask)
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{
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unsigned int len = skb_end_offset(skb);
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struct sk_buff *new;
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new = alloc_skb(len, gfp_mask);
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if (new == NULL)
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return NULL;
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NETLINK_CB(new).portid = NETLINK_CB(skb).portid;
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NETLINK_CB(new).dst_group = NETLINK_CB(skb).dst_group;
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NETLINK_CB(new).creds = NETLINK_CB(skb).creds;
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memcpy(skb_put(new, len), skb->data, len);
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return new;
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}
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int netlink_add_tap(struct netlink_tap *nt)
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{
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if (unlikely(nt->dev->type != ARPHRD_NETLINK))
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@ -206,7 +224,11 @@ static int __netlink_deliver_tap_skb(struct sk_buff *skb,
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int ret = -ENOMEM;
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dev_hold(dev);
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nskb = skb_clone(skb, GFP_ATOMIC);
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if (netlink_skb_is_mmaped(skb) || is_vmalloc_addr(skb->head))
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nskb = netlink_to_full_skb(skb, GFP_ATOMIC);
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else
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nskb = skb_clone(skb, GFP_ATOMIC);
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if (nskb) {
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nskb->dev = dev;
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nskb->protocol = htons((u16) sk->sk_protocol);
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@ -279,11 +301,6 @@ static void netlink_rcv_wake(struct sock *sk)
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}
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#ifdef CONFIG_NETLINK_MMAP
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static bool netlink_skb_is_mmaped(const struct sk_buff *skb)
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{
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return NETLINK_CB(skb).flags & NETLINK_SKB_MMAPED;
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}
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static bool netlink_rx_is_mmaped(struct sock *sk)
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{
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return nlk_sk(sk)->rx_ring.pg_vec != NULL;
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@ -846,7 +863,6 @@ static void netlink_ring_set_copied(struct sock *sk, struct sk_buff *skb)
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}
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#else /* CONFIG_NETLINK_MMAP */
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#define netlink_skb_is_mmaped(skb) false
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#define netlink_rx_is_mmaped(sk) false
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#define netlink_tx_is_mmaped(sk) false
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#define netlink_mmap sock_no_mmap
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@ -59,6 +59,15 @@ static inline struct netlink_sock *nlk_sk(struct sock *sk)
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return container_of(sk, struct netlink_sock, sk);
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}
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static inline bool netlink_skb_is_mmaped(const struct sk_buff *skb)
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{
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#ifdef CONFIG_NETLINK_MMAP
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return NETLINK_CB(skb).flags & NETLINK_SKB_MMAPED;
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#else
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return false;
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#endif /* CONFIG_NETLINK_MMAP */
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}
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struct netlink_table {
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struct rhashtable hash;
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struct hlist_head mc_list;
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