Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=f47b7257c7368698eabff6fd7b340071932af640
Commit:     f47b7257c7368698eabff6fd7b340071932af640
Parent:     9bf1d83e7ee653862ef740435a7f41e8fd6452a9
Author:     Jarek Poplawski <[EMAIL PROTECTED]>
AuthorDate: Sun Feb 17 22:31:19 2008 -0800
Committer:  David S. Miller <[EMAIL PROTECTED]>
CommitDate: Sun Feb 17 22:31:19 2008 -0800

    [AX25] ax25_out: check skb for NULL in ax25_kick()
    
    According to some OOPS reports ax25_kick tries to clone NULL skbs
    sometimes. It looks like a race with ax25_clear_queues(). Probably
    there is no need to add more than a simple check for this yet.
    Another report suggested there are probably also cases where ax25
    ->paclen == 0 can happen in ax25_output(); this wasn't confirmed
    during testing but let's leave this debugging check for some time.
    
    Reported-and-tested-by: Jann Traschewski <[EMAIL PROTECTED]>
    Signed-off-by: Jarek Poplawski <[EMAIL PROTECTED]>
    Signed-off-by: David S. Miller <[EMAIL PROTECTED]>
---
 net/ax25/ax25_out.c |   13 +++++++++++--
 1 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/net/ax25/ax25_out.c b/net/ax25/ax25_out.c
index 92b517a..bf706f8 100644
--- a/net/ax25/ax25_out.c
+++ b/net/ax25/ax25_out.c
@@ -117,6 +117,12 @@ void ax25_output(ax25_cb *ax25, int paclen, struct sk_buff 
*skb)
        unsigned char *p;
        int frontlen, len, fragno, ka9qfrag, first = 1;
 
+       if (paclen < 16) {
+               WARN_ON_ONCE(1);
+               kfree_skb(skb);
+               return;
+       }
+
        if ((skb->len - 1) > paclen) {
                if (*skb->data == AX25_P_TEXT) {
                        skb_pull(skb, 1); /* skip PID */
@@ -251,8 +257,6 @@ void ax25_kick(ax25_cb *ax25)
        if (start == end)
                return;
 
-       ax25->vs = start;
-
        /*
         * Transmit data until either we're out of data to send or
         * the window is full. Send a poll on the final I frame if
@@ -261,8 +265,13 @@ void ax25_kick(ax25_cb *ax25)
 
        /*
         * Dequeue the frame and copy it.
+        * Check for race with ax25_clear_queues().
         */
        skb  = skb_dequeue(&ax25->write_queue);
+       if (!skb)
+               return;
+
+       ax25->vs = start;
 
        do {
                if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
-
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