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Message-Id: <0bd907843b74bc2112ad960f7d11e75ca095eee3.1500998196.git.pabeni@redhat.com>
Date: Tue, 25 Jul 2017 17:57:47 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Paul Moore <paul@...l-moore.com>
Subject: [PATCH net] 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 0ddf3fb2c43d ("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@...l-moore.com>
Fixes: 0a463c78d25b ("udp: avoid a cache miss on dequeue")
Fixes: 0ddf3fb2c43d ("udp: preserve skb->dst if required for IP options processing")
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Tested-by: Paul Moore <paul@...l-moore.com>
---
include/net/udp.h | 33 ++++++++++++++++++++++-----------
net/ipv4/udp.c | 38 ++++++++++++++++++--------------------
2 files changed, 40 insertions(+), 31 deletions(-)
diff --git a/include/net/udp.h b/include/net/udp.h
index 972ce4baab6b..56ce2d2a612d 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -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
* possibly multiple cache miss on dequeue()
*/
-#if BITS_PER_LONG == 64
-
-/* truesize, len and the bit needed to compute skb_csum_unnecessary will be on
- * cold cache lines at recvmsg time.
- * skb->len can be stored on 16 bits since the udp header has been already
- * validated and pulled.
- */
struct udp_dev_scratch {
- u32 truesize;
+ /* 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;
+
+#if BITS_PER_LONG == 64
+ /* len and the bit needed to compute skb_csum_unnecessary
+ * will be on cold cache lines at recvmsg time.
+ * skb->len can be stored on 16 bits since the udp header has been
+ * already validated and pulled.
+ */
u16 len;
bool is_linear;
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)
{
- 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)
{
- 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)
{
- return ((struct udp_dev_scratch *)&skb->dev_scratch)->is_linear;
+ return udp_skb_scratch(skb)->is_linear;
}
#else
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index b057653ceca9..d243772f6efc 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1163,34 +1163,32 @@ int udp_sendpage(struct sock *sk, struct page *page, int offset,
return ret;
}
-#if BITS_PER_LONG == 64
+#define UDP_SKB_IS_STATELESS 0x80000000
+
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));
- scratch = (struct udp_dev_scratch *)&skb->dev_scratch;
- scratch->truesize = skb->truesize;
+ scratch->_tsize_state = skb->truesize;
+#if BITS_PER_LONG == 64
scratch->len = skb->len;
scratch->csum_unnecessary = !!skb_csum_unnecessary(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)
{
- return ((struct udp_dev_scratch *)&skb->dev_scratch)->truesize;
-}
-#else
-static void udp_set_dev_scratch(struct sk_buff *skb)
-{
- skb->dev_scratch = skb->truesize;
+ return udp_skb_scratch(skb)->_tsize_state & ~UDP_SKB_IS_STATELESS;
}
-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 */
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)
unlock_sock_fast(sk, slow);
}
- /* we cleared the head states previously only if the skb lacks any IP
- * options, see __udp_queue_rcv_skb().
+ /* In the more common cases we cleared the head states previously,
+ * 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);
consume_stateless_skb(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);
}
- /* At recvmsg() time we need skb->dst to process IP options-related
- * cmsg, elsewhere can we clear all pending head states while they are
- * hot in the cache
+ /* At recvmsg() time we may access skb->dst or skb->sp depending on
+ * the IP options and the cmsg flags, elsewhere can we clear all
+ * 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);
rc = __udp_enqueue_schedule_skb(sk, skb);
--
2.13.3
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