[PATCH v2] x25: remove the BKL

From: Arnd Bergmann
Date: Thu Jan 27 2011 - 07:38:49 EST

This replaces all instances of lock_kernel in x25
with lock_sock, taking care to release the socket
lock around sleeping functions (sock_alloc_send_skb
and skb_recv_datagram). It is not clear whether
this is a correct solution, but it seem to be what
other protocols do in the same situation.

Compile-tested only.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Andrew Hendry <andrew.hendry@xxxxxxxxx>
Cc: linux-x25@xxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx
---
v2: fix possible NULL-pointer dereference in x25_sendmsg

net/x25/Kconfig | 1 -
net/x25/af_x25.c | 58 ++++++++++++++++------------------------------------
net/x25/x25_out.c | 7 ++++-
3 files changed, 23 insertions(+), 43 deletions(-)

diff --git a/net/x25/Kconfig b/net/x25/Kconfig
index 2196e55..e6759c9 100644
--- a/net/x25/Kconfig
+++ b/net/x25/Kconfig
@@ -5,7 +5,6 @@
config X25
tristate "CCITT X.25 Packet Layer (EXPERIMENTAL)"
depends on EXPERIMENTAL
- depends on BKL # should be fixable
---help---
X.25 is a set of standardized network protocols, similar in scope to
frame relay; the one physical line from your box to the X.25 network
diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index ad96ee9..4680b1e 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -40,7 +40,6 @@
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/sched.h>
-#include <linux/smp_lock.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/net.h>
@@ -432,15 +431,6 @@ void x25_destroy_socket_from_timer(struct sock *sk)
sock_put(sk);
}

-static void x25_destroy_socket(struct sock *sk)
-{
- sock_hold(sk);
- lock_sock(sk);
- __x25_destroy_socket(sk);
- release_sock(sk);
- sock_put(sk);
-}
-
/*
* Handling for system calls applied via the various interfaces to a
* X.25 socket object.
@@ -647,18 +637,19 @@ static int x25_release(struct socket *sock)
struct sock *sk = sock->sk;
struct x25_sock *x25;

- lock_kernel();
if (!sk)
- goto out;
+ return 0;

x25 = x25_sk(sk);

+ sock_hold(sk);
+ lock_sock(sk);
switch (x25->state) {

case X25_STATE_0:
case X25_STATE_2:
x25_disconnect(sk, 0, 0, 0);
- x25_destroy_socket(sk);
+ __x25_destroy_socket(sk);
goto out;

case X25_STATE_1:
@@ -678,7 +669,8 @@ static int x25_release(struct socket *sock)

sock_orphan(sk);
out:
- unlock_kernel();
+ release_sock(sk);
+ sock_put(sk);
return 0;
}

@@ -1085,7 +1077,7 @@ static int x25_sendmsg(struct kiocb *iocb, struct socket *sock,
size_t size;
int qbit = 0, rc = -EINVAL;

- lock_kernel();
+ lock_sock(sk);
if (msg->msg_flags & ~(MSG_DONTWAIT|MSG_OOB|MSG_EOR|MSG_CMSG_COMPAT))
goto out;

@@ -1148,7 +1140,9 @@ static int x25_sendmsg(struct kiocb *iocb, struct socket *sock,

size = len + X25_MAX_L2_LEN + X25_EXT_MIN_LEN;

+ release_sock(sk);
skb = sock_alloc_send_skb(sk, size, noblock, &rc);
+ lock_sock(sk);
if (!skb)
goto out;
X25_SKB_CB(skb)->flags = msg->msg_flags;
@@ -1231,26 +1225,10 @@ static int x25_sendmsg(struct kiocb *iocb, struct socket *sock,
len++;
}

- /*
- * lock_sock() is currently only used to serialize this x25_kick()
- * against input-driven x25_kick() calls. It currently only blocks
- * incoming packets for this socket and does not protect against
- * any other socket state changes and is not called from anywhere
- * else. As x25_kick() cannot block and as long as all socket
- * operations are BKL-wrapped, we don't need take to care about
- * purging the backlog queue in x25_release().
- *
- * Using lock_sock() to protect all socket operations entirely
- * (and making the whole x25 stack SMP aware) unfortunately would
- * require major changes to {send,recv}msg and skb allocation methods.
- * -> 2.5 ;)
- */
- lock_sock(sk);
x25_kick(sk);
- release_sock(sk);
rc = len;
out:
- unlock_kernel();
+ release_sock(sk);
return rc;
out_kfree_skb:
kfree_skb(skb);
@@ -1271,7 +1249,7 @@ static int x25_recvmsg(struct kiocb *iocb, struct socket *sock,
unsigned char *asmptr;
int rc = -ENOTCONN;

- lock_kernel();
+ lock_sock(sk);
/*
* This works for seqpacket too. The receiver has ordered the queue for
* us! We do one quick check first though
@@ -1300,8 +1278,10 @@ static int x25_recvmsg(struct kiocb *iocb, struct socket *sock,
msg->msg_flags |= MSG_OOB;
} else {
/* Now we can treat all alike */
+ release_sock(sk);
skb = skb_recv_datagram(sk, flags & ~MSG_DONTWAIT,
flags & MSG_DONTWAIT, &rc);
+ lock_sock(sk);
if (!skb)
goto out;

@@ -1338,14 +1318,12 @@ static int x25_recvmsg(struct kiocb *iocb, struct socket *sock,

msg->msg_namelen = sizeof(struct sockaddr_x25);

- lock_sock(sk);
x25_check_rbuf(sk);
- release_sock(sk);
rc = copied;
out_free_dgram:
skb_free_datagram(sk, skb);
out:
- unlock_kernel();
+ release_sock(sk);
return rc;
}

@@ -1581,18 +1559,18 @@ out_cud_release:

case SIOCX25CALLACCPTAPPRV: {
rc = -EINVAL;
- lock_kernel();
+ lock_sock(sk);
if (sk->sk_state != TCP_CLOSE)
break;
clear_bit(X25_ACCPT_APPRV_FLAG, &x25->flags);
- unlock_kernel();
+ release_sock(sk);
rc = 0;
break;
}

case SIOCX25SENDCALLACCPT: {
rc = -EINVAL;
- lock_kernel();
+ lock_sock(sk);
if (sk->sk_state != TCP_ESTABLISHED)
break;
/* must call accptapprv above */
@@ -1600,7 +1578,7 @@ out_cud_release:
break;
x25_write_internal(sk, X25_CALL_ACCEPTED);
x25->state = X25_STATE_3;
- unlock_kernel();
+ release_sock(sk);
rc = 0;
break;
}
diff --git a/net/x25/x25_out.c b/net/x25/x25_out.c
index d00649f..f1a6ff1 100644
--- a/net/x25/x25_out.c
+++ b/net/x25/x25_out.c
@@ -68,8 +68,11 @@ int x25_output(struct sock *sk, struct sk_buff *skb)
frontlen = skb_headroom(skb);

while (skb->len > 0) {
- if ((skbn = sock_alloc_send_skb(sk, frontlen + max_len,
- noblock, &err)) == NULL){
+ release_sock(sk);
+ skbn = sock_alloc_send_skb(sk, frontlen + max_len,
+ 1, &err);
+ lock_sock(sk);
+ if (!skbn) {
if (err == -EWOULDBLOCK && noblock){
kfree_skb(skb);
return sent;
--
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