Re: [PATCH net v2 2/3] unix/dgram: fix peeking with an offset larger than data in queue

2013-04-29 Thread Cong Wang 
On Fri, 26 Apr 2013 at 18:35 GMT, Benjamin Poirier  wrote:
>  struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
> - int *peeked, int *off, int *err)
> + int *peeked, int *_off, int *err)
>  {
> - struct sk_buff *skb;
> + struct sk_buff *skb, *last;
>   long timeo;
>   /*
>* Caller is allowed not to check sk->sk_err before skb_recv_datagram()
> @@ -182,14 +183,17 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, 
> unsigned int flags,
>*/
>   unsigned long cpu_flags;
>   struct sk_buff_head *queue = >sk_receive_queue;
> + int off = *_off;
>  

Name the local variable '_off', not the function argument.
Or pick another name, e.g. 'offset'.

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Re: [PATCH net v2 2/3] unix/dgram: fix peeking with an offset larger than data in queue

2013-04-29 Thread Cong Wang 
On Fri, 26 Apr 2013 at 18:35 GMT, Benjamin Poirier bpoir...@suse.de wrote:
  struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
 - int *peeked, int *off, int *err)
 + int *peeked, int *_off, int *err)
  {
 - struct sk_buff *skb;
 + struct sk_buff *skb, *last;
   long timeo;
   /*
* Caller is allowed not to check sk-sk_err before skb_recv_datagram()
 @@ -182,14 +183,17 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, 
 unsigned int flags,
*/
   unsigned long cpu_flags;
   struct sk_buff_head *queue = sk-sk_receive_queue;
 + int off = *_off;
  

Name the local variable '_off', not the function argument.
Or pick another name, e.g. 'offset'.

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[PATCH net v2 2/3] unix/dgram: fix peeking with an offset larger than data in queue

2013-04-26 Thread Benjamin Poirier 
Currently, peeking on a unix datagram socket with an offset larger than len of
the data in the sk receive queue returns immediately with bogus data. That's
because *off is not reset between each skb_queue_walk().

This patch fixes this so that the behavior is the same as peeking with no
offset on an empty queue: the caller blocks.

Signed-off-by: Benjamin Poirier 
---

v2: address review feedback

 net/core/datagram.c |   27 ---
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 99c4f52..1985c9a 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -78,9 +78,10 @@ static int receiver_wake_function(wait_queue_t *wait, 
unsigned int mode, int syn
return autoremove_wake_function(wait, mode, sync, key);
 }
 /*
- * Wait for a packet..
+ * Wait for the last received packet to be different from skb
  */
-static int wait_for_packet(struct sock *sk, int *err, long *timeo_p)
+static int wait_for_more_packets(struct sock *sk, int *err, long *timeo_p,
+const struct sk_buff *skb)
 {
int error;
DEFINE_WAIT_FUNC(wait, receiver_wake_function);
@@ -92,7 +93,7 @@ static int wait_for_packet(struct sock *sk, int *err, long 
*timeo_p)
if (error)
goto out_err;
 
-   if (!skb_queue_empty(>sk_receive_queue))
+   if (sk->sk_receive_queue.prev != skb)
goto out;
 
/* Socket shut down? */
@@ -131,9 +132,9 @@ out_noerr:
  * __skb_recv_datagram - Receive a datagram skbuff
  * @sk: socket
  * @flags: MSG_ flags
- * @off: an offset in bytes to peek skb from. Returns an offset
- *   within an skb where data actually starts
  * @peeked: returns non-zero if this packet has been seen before
+ * @_off: an offset in bytes to peek skb from. Returns an offset
+ *within an skb where data actually starts
  * @err: error code returned
  *
  * Get a datagram skbuff, understands the peeking, nonblocking wakeups
@@ -159,9 +160,9 @@ out_noerr:
  * the standard around please.
  */
 struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
-   int *peeked, int *off, int *err)
+   int *peeked, int *_off, int *err)
 {
-   struct sk_buff *skb;
+   struct sk_buff *skb, *last;
long timeo;
/*
 * Caller is allowed not to check sk->sk_err before skb_recv_datagram()
@@ -182,14 +183,17 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, 
unsigned int flags,
 */
unsigned long cpu_flags;
struct sk_buff_head *queue = >sk_receive_queue;
+   int off = *_off;
 
+   last = (struct sk_buff *)queue;
spin_lock_irqsave(>lock, cpu_flags);
skb_queue_walk(queue, skb) {
+   last = skb;
*peeked = skb->peeked;
if (flags & MSG_PEEK) {
-   if (*off >= skb->len && (skb->len || *off ||
-skb->peeked)) {
-   *off -= skb->len;
+   if (off >= skb->len && (skb->len || off ||
+   skb->peeked)) {
+   off -= skb->len;
continue;
}
skb->peeked = 1;
@@ -198,6 +202,7 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, 
unsigned int flags,
__skb_unlink(skb, queue);
 
spin_unlock_irqrestore(>lock, cpu_flags);
+   *_off = off;
return skb;
}
spin_unlock_irqrestore(>lock, cpu_flags);
@@ -207,7 +212,7 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, 
unsigned int flags,
if (!timeo)
goto no_packet;
 
-   } while (!wait_for_packet(sk, err, ));
+   } while (!wait_for_more_packets(sk, err, , last));
 
return NULL;
 
-- 
1.7.10.4

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[PATCH net v2 2/3] unix/dgram: fix peeking with an offset larger than data in queue

2013-04-26 Thread Benjamin Poirier 
Currently, peeking on a unix datagram socket with an offset larger than len of
the data in the sk receive queue returns immediately with bogus data. That's
because *off is not reset between each skb_queue_walk().

This patch fixes this so that the behavior is the same as peeking with no
offset on an empty queue: the caller blocks.

Signed-off-by: Benjamin Poirier bpoir...@suse.de
---

v2: address review feedback

 net/core/datagram.c |   27 ---
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 99c4f52..1985c9a 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -78,9 +78,10 @@ static int receiver_wake_function(wait_queue_t *wait, 
unsigned int mode, int syn
return autoremove_wake_function(wait, mode, sync, key);
 }
 /*
- * Wait for a packet..
+ * Wait for the last received packet to be different from skb
  */
-static int wait_for_packet(struct sock *sk, int *err, long *timeo_p)
+static int wait_for_more_packets(struct sock *sk, int *err, long *timeo_p,
+const struct sk_buff *skb)
 {
int error;
DEFINE_WAIT_FUNC(wait, receiver_wake_function);
@@ -92,7 +93,7 @@ static int wait_for_packet(struct sock *sk, int *err, long 
*timeo_p)
if (error)
goto out_err;
 
-   if (!skb_queue_empty(sk-sk_receive_queue))
+   if (sk-sk_receive_queue.prev != skb)
goto out;
 
/* Socket shut down? */
@@ -131,9 +132,9 @@ out_noerr:
  * __skb_recv_datagram - Receive a datagram skbuff
  * @sk: socket
  * @flags: MSG_ flags
- * @off: an offset in bytes to peek skb from. Returns an offset
- *   within an skb where data actually starts
  * @peeked: returns non-zero if this packet has been seen before
+ * @_off: an offset in bytes to peek skb from. Returns an offset
+ *within an skb where data actually starts
  * @err: error code returned
  *
  * Get a datagram skbuff, understands the peeking, nonblocking wakeups
@@ -159,9 +160,9 @@ out_noerr:
  * the standard around please.
  */
 struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
-   int *peeked, int *off, int *err)
+   int *peeked, int *_off, int *err)
 {
-   struct sk_buff *skb;
+   struct sk_buff *skb, *last;
long timeo;
/*
 * Caller is allowed not to check sk-sk_err before skb_recv_datagram()
@@ -182,14 +183,17 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, 
unsigned int flags,
 */
unsigned long cpu_flags;
struct sk_buff_head *queue = sk-sk_receive_queue;
+   int off = *_off;
 
+   last = (struct sk_buff *)queue;
spin_lock_irqsave(queue-lock, cpu_flags);
skb_queue_walk(queue, skb) {
+   last = skb;
*peeked = skb-peeked;
if (flags  MSG_PEEK) {
-   if (*off = skb-len  (skb-len || *off ||
-skb-peeked)) {
-   *off -= skb-len;
+   if (off = skb-len  (skb-len || off ||
+   skb-peeked)) {
+   off -= skb-len;
continue;
}
skb-peeked = 1;
@@ -198,6 +202,7 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, 
unsigned int flags,
__skb_unlink(skb, queue);
 
spin_unlock_irqrestore(queue-lock, cpu_flags);
+   *_off = off;
return skb;
}
spin_unlock_irqrestore(queue-lock, cpu_flags);
@@ -207,7 +212,7 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, 
unsigned int flags,
if (!timeo)
goto no_packet;
 
-   } while (!wait_for_packet(sk, err, timeo));
+   } while (!wait_for_more_packets(sk, err, timeo, last));
 
return NULL;
 
-- 
1.7.10.4

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