From 7f502361531e9eecb396cf99bdc9e9a59f7ebd7f Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 30 Jun 2014 01:26:23 -0700 Subject: ipv4: irq safe sk_dst_[re]set() and ipv4_sk_update_pmtu() fix We have two different ways to handle changes to sk->sk_dst First way (used by TCP) assumes socket lock is owned by caller, and use no extra lock : __sk_dst_set() & __sk_dst_reset() Another way (used by UDP) uses sk_dst_lock because socket lock is not always taken. Note that sk_dst_lock is not softirq safe. These ways are not inter changeable for a given socket type. ipv4_sk_update_pmtu(), added in linux-3.8, added a race, as it used the socket lock as synchronization, but users might be UDP sockets. Instead of converting sk_dst_lock to a softirq safe version, use xchg() as we did for sk_rx_dst in commit e47eb5dfb296b ("udp: ipv4: do not use sk_dst_lock from softirq context") In a follow up patch, we probably can remove sk_dst_lock, as it is only used in IPv6. Signed-off-by: Eric Dumazet Cc: Steffen Klassert Fixes: 9cb3a50c5f63e ("ipv4: Invalidate the socket cached route on pmtu events if possible") Signed-off-by: David S. Miller --- include/net/sock.h | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'include/net') diff --git a/include/net/sock.h b/include/net/sock.h index 173cae4..c556fd9 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1768,9 +1768,11 @@ __sk_dst_set(struct sock *sk, struct dst_entry *dst) static inline void sk_dst_set(struct sock *sk, struct dst_entry *dst) { - spin_lock(&sk->sk_dst_lock); - __sk_dst_set(sk, dst); - spin_unlock(&sk->sk_dst_lock); + struct dst_entry *old_dst; + + sk_tx_queue_clear(sk); + old_dst = xchg(&sk->sk_dst_cache, dst); + dst_release(old_dst); } static inline void @@ -1782,9 +1784,7 @@ __sk_dst_reset(struct sock *sk) static inline void sk_dst_reset(struct sock *sk) { - spin_lock(&sk->sk_dst_lock); - __sk_dst_reset(sk); - spin_unlock(&sk->sk_dst_lock); + sk_dst_set(sk, NULL); } struct dst_entry *__sk_dst_check(struct sock *sk, u32 cookie); -- cgit v1.1