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udp: preserve head state for IP_CMSG_PASSSEC
Paul Moore reported a SELinux/IP_PASSSEC regression caused by missing skb->sp at recvmsg() time. We need to preserve the skb head state to process the IP_CMSG_PASSSEC cmsg. With this commit we avoid releasing the skb head state in the BH even if a secpath is attached to the current skb, and stores the skb status (with/without head states) in the scratch area, so that we can access it at skb deallocation time, without incurring in cache-miss penalties. This also avoids misusing the skb CB for ipv6 packets, as introduced by the commit0ddf3fb2c4
("udp: preserve skb->dst if required for IP options processing"). Clean a bit the scratch area helpers implementation, to reduce the code differences between 32 and 64 bits build. Reported-by: Paul Moore <paul@paul-moore.com> Fixes:0a463c78d2
("udp: avoid a cache miss on dequeue") Fixes:0ddf3fb2c4
("udp: preserve skb->dst if required for IP options processing") Signed-off-by: Paolo Abeni <pabeni@redhat.com> Tested-by: Paul Moore <paul@paul-moore.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
parent
9f9e772da2
commit
dce4551cb2
2 changed files with 47 additions and 38 deletions
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@ -305,33 +305,44 @@ struct sock *udp6_lib_lookup_skb(struct sk_buff *skb,
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/* UDP uses skb->dev_scratch to cache as much information as possible and avoid
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* possibly multiple cache miss on dequeue()
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*/
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#if BITS_PER_LONG == 64
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/* truesize, len and the bit needed to compute skb_csum_unnecessary will be on
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* cold cache lines at recvmsg time.
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* skb->len can be stored on 16 bits since the udp header has been already
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* validated and pulled.
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*/
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struct udp_dev_scratch {
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u32 truesize;
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/* skb->truesize and the stateless bit are embedded in a single field;
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* do not use a bitfield since the compiler emits better/smaller code
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* this way
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*/
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u32 _tsize_state;
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#if BITS_PER_LONG == 64
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/* len and the bit needed to compute skb_csum_unnecessary
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* will be on cold cache lines at recvmsg time.
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* skb->len can be stored on 16 bits since the udp header has been
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* already validated and pulled.
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*/
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u16 len;
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bool is_linear;
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bool csum_unnecessary;
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#endif
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};
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static inline struct udp_dev_scratch *udp_skb_scratch(struct sk_buff *skb)
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{
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return (struct udp_dev_scratch *)&skb->dev_scratch;
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}
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#if BITS_PER_LONG == 64
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static inline unsigned int udp_skb_len(struct sk_buff *skb)
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{
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return ((struct udp_dev_scratch *)&skb->dev_scratch)->len;
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return udp_skb_scratch(skb)->len;
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}
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static inline bool udp_skb_csum_unnecessary(struct sk_buff *skb)
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{
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return ((struct udp_dev_scratch *)&skb->dev_scratch)->csum_unnecessary;
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return udp_skb_scratch(skb)->csum_unnecessary;
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}
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static inline bool udp_skb_is_linear(struct sk_buff *skb)
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{
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return ((struct udp_dev_scratch *)&skb->dev_scratch)->is_linear;
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return udp_skb_scratch(skb)->is_linear;
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}
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#else
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@ -1163,34 +1163,32 @@ int udp_sendpage(struct sock *sk, struct page *page, int offset,
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return ret;
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}
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#if BITS_PER_LONG == 64
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#define UDP_SKB_IS_STATELESS 0x80000000
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static void udp_set_dev_scratch(struct sk_buff *skb)
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{
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struct udp_dev_scratch *scratch;
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struct udp_dev_scratch *scratch = udp_skb_scratch(skb);
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BUILD_BUG_ON(sizeof(struct udp_dev_scratch) > sizeof(long));
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scratch = (struct udp_dev_scratch *)&skb->dev_scratch;
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scratch->truesize = skb->truesize;
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scratch->_tsize_state = skb->truesize;
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#if BITS_PER_LONG == 64
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scratch->len = skb->len;
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scratch->csum_unnecessary = !!skb_csum_unnecessary(skb);
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scratch->is_linear = !skb_is_nonlinear(skb);
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}
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static int udp_skb_truesize(struct sk_buff *skb)
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{
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return ((struct udp_dev_scratch *)&skb->dev_scratch)->truesize;
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}
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#else
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static void udp_set_dev_scratch(struct sk_buff *skb)
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{
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skb->dev_scratch = skb->truesize;
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}
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static int udp_skb_truesize(struct sk_buff *skb)
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{
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return skb->dev_scratch;
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}
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#endif
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if (likely(!skb->_skb_refdst))
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scratch->_tsize_state |= UDP_SKB_IS_STATELESS;
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}
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static int udp_skb_truesize(struct sk_buff *skb)
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{
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return udp_skb_scratch(skb)->_tsize_state & ~UDP_SKB_IS_STATELESS;
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}
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static bool udp_skb_has_head_state(struct sk_buff *skb)
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{
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return !(udp_skb_scratch(skb)->_tsize_state & UDP_SKB_IS_STATELESS);
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}
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/* fully reclaim rmem/fwd memory allocated for skb */
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static void udp_rmem_release(struct sock *sk, int size, int partial,
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@ -1388,10 +1386,10 @@ void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len)
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unlock_sock_fast(sk, slow);
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}
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/* we cleared the head states previously only if the skb lacks any IP
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* options, see __udp_queue_rcv_skb().
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/* In the more common cases we cleared the head states previously,
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* see __udp_queue_rcv_skb().
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*/
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if (unlikely(IPCB(skb)->opt.optlen > 0))
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if (unlikely(udp_skb_has_head_state(skb)))
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skb_release_head_state(skb);
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consume_stateless_skb(skb);
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}
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@ -1784,11 +1782,11 @@ static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
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sk_mark_napi_id_once(sk, skb);
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}
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/* At recvmsg() time we need skb->dst to process IP options-related
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* cmsg, elsewhere can we clear all pending head states while they are
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* hot in the cache
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/* At recvmsg() time we may access skb->dst or skb->sp depending on
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* the IP options and the cmsg flags, elsewhere can we clear all
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* pending head states while they are hot in the cache
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*/
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if (likely(IPCB(skb)->opt.optlen == 0))
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if (likely(IPCB(skb)->opt.optlen == 0 && !skb->sp))
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skb_release_head_state(skb);
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rc = __udp_enqueue_schedule_skb(sk, skb);
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