1 files changed, 44 insertions, 13 deletions

diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index c8231fb15708..3308fd7f1b52 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -349,25 +349,47 @@ static int parse(struct nlattr *na, struct cpumask *mask)
         return ret;
 }
 
+#ifdef CONFIG_IA64
+#define TASKSTATS_NEEDS_PADDING 1
+#endif
+
 static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid)
 {
         struct nlattr *na, *ret;
         int aggr;
 
-        /* If we don't pad, we end up with alignment on a 4 byte boundary.
-         * This causes lots of runtime warnings on systems requiring 8 byte
-         * alignment */
-        u32 pids[2] = { pid, 0 };
-        int pid_size = ALIGN(sizeof(pid), sizeof(long));
-
         aggr = (type == TASKSTATS_TYPE_PID)
                         ? TASKSTATS_TYPE_AGGR_PID
                         : TASKSTATS_TYPE_AGGR_TGID;
 
+        /*
+         * The taskstats structure is internally aligned on 8 byte
+         * boundaries but the layout of the aggregrate reply, with
+         * two NLA headers and the pid (each 4 bytes), actually
+         * force the entire structure to be unaligned. This causes
+         * the kernel to issue unaligned access warnings on some
+         * architectures like ia64. Unfortunately, some software out there
+         * doesn't properly unroll the NLA packet and assumes that the start
+         * of the taskstats structure will always be 20 bytes from the start
+         * of the netlink payload. Aligning the start of the taskstats
+         * structure breaks this software, which we don't want. So, for now
+         * the alignment only happens on architectures that require it
+         * and those users will have to update to fixed versions of those
+         * packages. Space is reserved in the packet only when needed.
+         * This ifdef should be removed in several years e.g. 2012 once
+         * we can be confident that fixed versions are installed on most
+         * systems. We add the padding before the aggregate since the
+         * aggregate is already a defined type.
+         */
+#ifdef TASKSTATS_NEEDS_PADDING
+        if (nla_put(skb, TASKSTATS_TYPE_NULL, 0, NULL) < 0)
+                goto err;
+#endif
         na = nla_nest_start(skb, aggr);
         if (!na)
                 goto err;
-        if (nla_put(skb, type, pid_size, pids) < 0)
+
+        if (nla_put(skb, type, sizeof(pid), &pid) < 0)
                 goto err;
         ret = nla_reserve(skb, TASKSTATS_TYPE_STATS, sizeof(struct taskstats));
         if (!ret)
@@ -456,6 +478,18 @@ out:
         return rc;
 }
 
+static size_t taskstats_packet_size(void)
+{
+        size_t size;
+
+        size = nla_total_size(sizeof(u32)) +
+                nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
+#ifdef TASKSTATS_NEEDS_PADDING
+        size += nla_total_size(0); /* Padding for alignment */
+#endif
+        return size;
+}
+
 static int cmd_attr_pid(struct genl_info *info)
 {
         struct taskstats *stats;
@@ -464,8 +498,7 @@ static int cmd_attr_pid(struct genl_info *info)
         u32 pid;
         int rc;
 
-        size = nla_total_size(sizeof(u32)) +
-                nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
+        size = taskstats_packet_size();
 
         rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, size);
         if (rc < 0)
@@ -494,8 +527,7 @@ static int cmd_attr_tgid(struct genl_info *info)
         u32 tgid;
         int rc;
 
-        size = nla_total_size(sizeof(u32)) +
-                nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
+        size = taskstats_packet_size();
 
         rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, size);
         if (rc < 0)
@@ -570,8 +602,7 @@ void taskstats_exit(struct task_struct *tsk, int group_dead)
         /*
          * Size includes space for nested attributes
          */
-        size = nla_total_size(sizeof(u32)) +
-                nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
+        size = taskstats_packet_size();
 
         is_thread_group = !!taskstats_tgid_alloc(tsk);
         if (is_thread_group) {