[PATCH][ATM]: [clip] fix race between modifying entry->vccs and clip_start_xmit()

[chas williams <chas@xxxxxxxxxxxxxxxx>]

please apply to 2.6 and 2.4 -- thanks

# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
#                  ChangeSet    1.1315  -> 1.1316 
#             net/atm/clip.c    1.22    -> 1.23   
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 03/09/15      chas@xxxxxxxxxxxxxxxxxxxxxx     1.1316
# [ATM]: [clip] fix race between modifying entry->vccs and clip_start_xmit()
# --------------------------------------------
#
diff -Nru a/net/atm/clip.c b/net/atm/clip.c
--- a/net/atm/clip.c    Mon Sep 15 15:08:57 2003
+++ b/net/atm/clip.c    Mon Sep 15 15:08:57 2003
@@ -93,6 +93,7 @@
                printk(KERN_CRIT "!clip_vcc->entry (clip_vcc %p)\n",clip_vcc);
                return;
        }
+       spin_lock_bh(&entry->neigh->dev->xmit_lock);    /* block 
clip_start_xmit() */
        entry->neigh->used = jiffies;
        for (walk = &entry->vccs; *walk; walk = &(*walk)->next)
                if (*walk == clip_vcc) {
@@ -102,17 +103,20 @@
                        clip_vcc->entry = NULL;
                        if (clip_vcc->xoff)
                                netif_wake_queue(entry->neigh->dev);
-                       if (entry->vccs) return;
+                       if (entry->vccs)
+                               goto out;
                        entry->expires = jiffies-1;
                                /* force resolution or expiration */
                        error = neigh_update(entry->neigh,NULL,NUD_NONE,0,0);
                        if (error)
                                printk(KERN_CRIT "unlink_clip_vcc: "
                                    "neigh_update failed with %d\n",error);
-                       return;
+                       goto out;
                }
        printk(KERN_CRIT "ATMARP: unlink_clip_vcc failed (entry %p, vcc "
          "0x%p)\n",entry,clip_vcc);
+out:
+       spin_unlock_bh(&entry->neigh->dev->xmit_lock);
 }