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authorEric Dumazet <eric.dumazet@gmail.com>2014-03-10 09:50:11 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-04-14 06:42:16 -0700
commitcbbb5a252da5584e9a48e412e69ea09b4dd34cac (patch)
treefdf6d57604f47eaca9eadd72765f75eee2c3686d
parent471e50f30749fbd9a410b29b6549aa26f76fc021 (diff)
downloadlinux-linaro-stable-cbbb5a252da5584e9a48e412e69ea09b4dd34cac.tar.gz
tcp: tcp_release_cb() should release socket ownership
[ Upstream commit c3f9b01849ef3bc69024990092b9f42e20df7797 ] Lars Persson reported following deadlock : -000 |M:0x0:0x802B6AF8(asm) <-- arch_spin_lock -001 |tcp_v4_rcv(skb = 0x8BD527A0) <-- sk = 0x8BE6B2A0 -002 |ip_local_deliver_finish(skb = 0x8BD527A0) -003 |__netif_receive_skb_core(skb = 0x8BD527A0, ?) -004 |netif_receive_skb(skb = 0x8BD527A0) -005 |elk_poll(napi = 0x8C770500, budget = 64) -006 |net_rx_action(?) -007 |__do_softirq() -008 |do_softirq() -009 |local_bh_enable() -010 |tcp_rcv_established(sk = 0x8BE6B2A0, skb = 0x87D3A9E0, th = 0x814EBE14, ?) -011 |tcp_v4_do_rcv(sk = 0x8BE6B2A0, skb = 0x87D3A9E0) -012 |tcp_delack_timer_handler(sk = 0x8BE6B2A0) -013 |tcp_release_cb(sk = 0x8BE6B2A0) -014 |release_sock(sk = 0x8BE6B2A0) -015 |tcp_sendmsg(?, sk = 0x8BE6B2A0, ?, ?) -016 |sock_sendmsg(sock = 0x8518C4C0, msg = 0x87D8DAA8, size = 4096) -017 |kernel_sendmsg(?, ?, ?, ?, size = 4096) -018 |smb_send_kvec() -019 |smb_send_rqst(server = 0x87C4D400, rqst = 0x87D8DBA0) -020 |cifs_call_async() -021 |cifs_async_writev(wdata = 0x87FD6580) -022 |cifs_writepages(mapping = 0x852096E4, wbc = 0x87D8DC88) -023 |__writeback_single_inode(inode = 0x852095D0, wbc = 0x87D8DC88) -024 |writeback_sb_inodes(sb = 0x87D6D800, wb = 0x87E4A9C0, work = 0x87D8DD88) -025 |__writeback_inodes_wb(wb = 0x87E4A9C0, work = 0x87D8DD88) -026 |wb_writeback(wb = 0x87E4A9C0, work = 0x87D8DD88) -027 |wb_do_writeback(wb = 0x87E4A9C0, force_wait = 0) -028 |bdi_writeback_workfn(work = 0x87E4A9CC) -029 |process_one_work(worker = 0x8B045880, work = 0x87E4A9CC) -030 |worker_thread(__worker = 0x8B045880) -031 |kthread(_create = 0x87CADD90) -032 |ret_from_kernel_thread(asm) Bug occurs because __tcp_checksum_complete_user() enables BH, assuming it is running from softirq context. Lars trace involved a NIC without RX checksum support but other points are problematic as well, like the prequeue stuff. Problem is triggered by a timer, that found socket being owned by user. tcp_release_cb() should call tcp_write_timer_handler() or tcp_delack_timer_handler() in the appropriate context : BH disabled and socket lock held, but 'owned' field cleared, as if they were running from timer handlers. Fixes: 6f458dfb4092 ("tcp: improve latencies of timer triggered events") Reported-by: Lars Persson <lars.persson@axis.com> Tested-by: Lars Persson <lars.persson@axis.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--include/net/sock.h5
-rw-r--r--net/core/sock.c5
-rw-r--r--net/ipv4/tcp_output.c11
3 files changed, 20 insertions, 1 deletions
diff --git a/include/net/sock.h b/include/net/sock.h
index cec4c723db9a..8f32b779bc83 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1437,6 +1437,11 @@ static inline void sk_wmem_free_skb(struct sock *sk, struct sk_buff *skb)
*/
#define sock_owned_by_user(sk) ((sk)->sk_lock.owned)
+static inline void sock_release_ownership(struct sock *sk)
+{
+ sk->sk_lock.owned = 0;
+}
+
/*
* Macro so as to not evaluate some arguments when
* lockdep is not enabled.
diff --git a/net/core/sock.c b/net/core/sock.c
index 3ba527074f7f..d743099250f4 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2309,10 +2309,13 @@ void release_sock(struct sock *sk)
if (sk->sk_backlog.tail)
__release_sock(sk);
+ /* Warning : release_cb() might need to release sk ownership,
+ * ie call sock_release_ownership(sk) before us.
+ */
if (sk->sk_prot->release_cb)
sk->sk_prot->release_cb(sk);
- sk->sk_lock.owned = 0;
+ sock_release_ownership(sk);
if (waitqueue_active(&sk->sk_lock.wq))
wake_up(&sk->sk_lock.wq);
spin_unlock_bh(&sk->sk_lock.slock);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 6da3d94a114b..4a4e8746d1b2 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -755,6 +755,17 @@ void tcp_release_cb(struct sock *sk)
if (flags & (1UL << TCP_TSQ_DEFERRED))
tcp_tsq_handler(sk);
+ /* Here begins the tricky part :
+ * We are called from release_sock() with :
+ * 1) BH disabled
+ * 2) sk_lock.slock spinlock held
+ * 3) socket owned by us (sk->sk_lock.owned == 1)
+ *
+ * But following code is meant to be called from BH handlers,
+ * so we should keep BH disabled, but early release socket ownership
+ */
+ sock_release_ownership(sk);
+
if (flags & (1UL << TCP_WRITE_TIMER_DEFERRED)) {
tcp_write_timer_handler(sk);
__sock_put(sk);