Commit dce4551c authored by Paolo Abeni's avatar Paolo Abeni Committed by David S. Miller

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 commit 0ddf3fb2 ("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: default avatarPaul Moore <paul@paul-moore.com>
Fixes: 0a463c78 ("udp: avoid a cache miss on dequeue")
Fixes: 0ddf3fb2 ("udp: preserve skb->dst if required for IP options processing")
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Tested-by: default avatarPaul Moore <paul@paul-moore.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9f9e772d
...@@ -305,33 +305,44 @@ struct sock *udp6_lib_lookup_skb(struct sk_buff *skb, ...@@ -305,33 +305,44 @@ struct sock *udp6_lib_lookup_skb(struct sk_buff *skb,
/* UDP uses skb->dev_scratch to cache as much information as possible and avoid /* UDP uses skb->dev_scratch to cache as much information as possible and avoid
* possibly multiple cache miss on dequeue() * possibly multiple cache miss on dequeue()
*/ */
#if BITS_PER_LONG == 64 struct udp_dev_scratch {
/* skb->truesize and the stateless bit are embedded in a single field;
* do not use a bitfield since the compiler emits better/smaller code
* this way
*/
u32 _tsize_state;
/* truesize, len and the bit needed to compute skb_csum_unnecessary will be on #if BITS_PER_LONG == 64
* cold cache lines at recvmsg time. /* len and the bit needed to compute skb_csum_unnecessary
* skb->len can be stored on 16 bits since the udp header has been already * will be on cold cache lines at recvmsg time.
* validated and pulled. * skb->len can be stored on 16 bits since the udp header has been
* already validated and pulled.
*/ */
struct udp_dev_scratch {
u32 truesize;
u16 len; u16 len;
bool is_linear; bool is_linear;
bool csum_unnecessary; bool csum_unnecessary;
#endif
}; };
static inline struct udp_dev_scratch *udp_skb_scratch(struct sk_buff *skb)
{
return (struct udp_dev_scratch *)&skb->dev_scratch;
}
#if BITS_PER_LONG == 64
static inline unsigned int udp_skb_len(struct sk_buff *skb) static inline unsigned int udp_skb_len(struct sk_buff *skb)
{ {
return ((struct udp_dev_scratch *)&skb->dev_scratch)->len; return udp_skb_scratch(skb)->len;
} }
static inline bool udp_skb_csum_unnecessary(struct sk_buff *skb) static inline bool udp_skb_csum_unnecessary(struct sk_buff *skb)
{ {
return ((struct udp_dev_scratch *)&skb->dev_scratch)->csum_unnecessary; return udp_skb_scratch(skb)->csum_unnecessary;
} }
static inline bool udp_skb_is_linear(struct sk_buff *skb) static inline bool udp_skb_is_linear(struct sk_buff *skb)
{ {
return ((struct udp_dev_scratch *)&skb->dev_scratch)->is_linear; return udp_skb_scratch(skb)->is_linear;
} }
#else #else
......
...@@ -1163,34 +1163,32 @@ int udp_sendpage(struct sock *sk, struct page *page, int offset, ...@@ -1163,34 +1163,32 @@ int udp_sendpage(struct sock *sk, struct page *page, int offset,
return ret; return ret;
} }
#if BITS_PER_LONG == 64 #define UDP_SKB_IS_STATELESS 0x80000000
static void udp_set_dev_scratch(struct sk_buff *skb) static void udp_set_dev_scratch(struct sk_buff *skb)
{ {
struct udp_dev_scratch *scratch; struct udp_dev_scratch *scratch = udp_skb_scratch(skb);
BUILD_BUG_ON(sizeof(struct udp_dev_scratch) > sizeof(long)); BUILD_BUG_ON(sizeof(struct udp_dev_scratch) > sizeof(long));
scratch = (struct udp_dev_scratch *)&skb->dev_scratch; scratch->_tsize_state = skb->truesize;
scratch->truesize = skb->truesize; #if BITS_PER_LONG == 64
scratch->len = skb->len; scratch->len = skb->len;
scratch->csum_unnecessary = !!skb_csum_unnecessary(skb); scratch->csum_unnecessary = !!skb_csum_unnecessary(skb);
scratch->is_linear = !skb_is_nonlinear(skb); scratch->is_linear = !skb_is_nonlinear(skb);
#endif
if (likely(!skb->_skb_refdst))
scratch->_tsize_state |= UDP_SKB_IS_STATELESS;
} }
static int udp_skb_truesize(struct sk_buff *skb) static int udp_skb_truesize(struct sk_buff *skb)
{ {
return ((struct udp_dev_scratch *)&skb->dev_scratch)->truesize; return udp_skb_scratch(skb)->_tsize_state & ~UDP_SKB_IS_STATELESS;
}
#else
static void udp_set_dev_scratch(struct sk_buff *skb)
{
skb->dev_scratch = skb->truesize;
} }
static int udp_skb_truesize(struct sk_buff *skb) static bool udp_skb_has_head_state(struct sk_buff *skb)
{ {
return skb->dev_scratch; return !(udp_skb_scratch(skb)->_tsize_state & UDP_SKB_IS_STATELESS);
} }
#endif
/* fully reclaim rmem/fwd memory allocated for skb */ /* fully reclaim rmem/fwd memory allocated for skb */
static void udp_rmem_release(struct sock *sk, int size, int partial, static void udp_rmem_release(struct sock *sk, int size, int partial,
...@@ -1388,10 +1386,10 @@ void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len) ...@@ -1388,10 +1386,10 @@ void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len)
unlock_sock_fast(sk, slow); unlock_sock_fast(sk, slow);
} }
/* we cleared the head states previously only if the skb lacks any IP /* In the more common cases we cleared the head states previously,
* options, see __udp_queue_rcv_skb(). * see __udp_queue_rcv_skb().
*/ */
if (unlikely(IPCB(skb)->opt.optlen > 0)) if (unlikely(udp_skb_has_head_state(skb)))
skb_release_head_state(skb); skb_release_head_state(skb);
consume_stateless_skb(skb); consume_stateless_skb(skb);
} }
...@@ -1784,11 +1782,11 @@ static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb) ...@@ -1784,11 +1782,11 @@ static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
sk_mark_napi_id_once(sk, skb); sk_mark_napi_id_once(sk, skb);
} }
/* At recvmsg() time we need skb->dst to process IP options-related /* At recvmsg() time we may access skb->dst or skb->sp depending on
* cmsg, elsewhere can we clear all pending head states while they are * the IP options and the cmsg flags, elsewhere can we clear all
* hot in the cache * pending head states while they are hot in the cache
*/ */
if (likely(IPCB(skb)->opt.optlen == 0)) if (likely(IPCB(skb)->opt.optlen == 0 && !skb->sp))
skb_release_head_state(skb); skb_release_head_state(skb);
rc = __udp_enqueue_schedule_skb(sk, skb); rc = __udp_enqueue_schedule_skb(sk, skb);
......
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