[PATCH] taskstats: cleanup reply assembling

Thomas Graf wrote:
>
> nla_nest_start() may return NULL, either rely on prepare_reply() to be
> correct and BUG() on failure or do proper error handling for all
> functions.

nla_put() in taskstat.c can fail only if the 'size' argument of alloc_skb()
was not right. This is a kernel bug, we should not hide it. So add 'BUG()'
on error path and check for 'na == NULL'.

> genlmsg_cancel() is only required in error paths for dumping
> procedures.

So we can remove 'genlmsg_cancel()' calls and 'void *reply' (saves 227 bytes).

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: Shailabh Nagar <nagar@watson.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Jay Lan <jlan@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 16 insertions, 22 deletions

diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index b0aad99c4f8d..4c3476fa058d 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -69,7 +69,7 @@ enum actions {
 };
 
 static int prepare_reply(struct genl_info *info, u8 cmd, struct sk_buff **skbp,
-                        void **replyp, size_t size)
+                                size_t size)
 {
         struct sk_buff *skb;
         void *reply;
@@ -94,7 +94,6 @@ static int prepare_reply(struct genl_info *info, u8 cmd, struct sk_buff **skbp,
         }
 
         *skbp = skb;
-        *replyp = reply;
         return 0;
 }
 
@@ -351,11 +350,13 @@ static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid)
         struct nlattr *na, *ret;
         int aggr;
 
-        aggr = TASKSTATS_TYPE_AGGR_TGID;
-        if (type == TASKSTATS_TYPE_PID)
-                aggr = TASKSTATS_TYPE_AGGR_PID;
+        aggr = (type == TASKSTATS_TYPE_PID)
+                        ? TASKSTATS_TYPE_AGGR_PID
+                        : TASKSTATS_TYPE_AGGR_TGID;
 
         na = nla_nest_start(skb, aggr);
+        if (!na)
+                goto err;
         if (nla_put(skb, type, sizeof(pid), &pid) < 0)
                 goto err;
         ret = nla_reserve(skb, TASKSTATS_TYPE_STATS, sizeof(struct taskstats));
@@ -373,7 +374,6 @@ static int taskstats_user_cmd(struct sk_buff *skb, struct genl_info *info)
         int rc = 0;
         struct sk_buff *rep_skb;
         struct taskstats *stats;
-        void *reply;
         size_t size;
         cpumask_t mask;
 
@@ -395,7 +395,7 @@ static int taskstats_user_cmd(struct sk_buff *skb, struct genl_info *info)
         size = nla_total_size(sizeof(u32)) +
                 nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
 
-        rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, &reply, size);
+        rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, size);
         if (rc < 0)
                 return rc;
 
@@ -404,27 +404,24 @@ static int taskstats_user_cmd(struct sk_buff *skb, struct genl_info *info)
                 u32 pid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_PID]);
                 stats = mk_reply(rep_skb, TASKSTATS_TYPE_PID, pid);
                 if (!stats)
-                        goto nla_err;
+                        goto err;
 
                 rc = fill_pid(pid, NULL, stats);
                 if (rc < 0)
-                        goto nla_err;
+                        goto err;
         } else if (info->attrs[TASKSTATS_CMD_ATTR_TGID]) {
                 u32 tgid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_TGID]);
                 stats = mk_reply(rep_skb, TASKSTATS_TYPE_TGID, tgid);
                 if (!stats)
-                        goto nla_err;
+                        goto err;
 
                 rc = fill_tgid(tgid, NULL, stats);
                 if (rc < 0)
-                        goto nla_err;
+                        goto err;
         } else
                 goto err;
 
         return send_reply(rep_skb, info->snd_pid);
-
-nla_err:
-        genlmsg_cancel(rep_skb, reply);
 err:
         nlmsg_free(rep_skb);
         return rc;
@@ -461,7 +458,6 @@ void taskstats_exit(struct task_struct *tsk, int group_dead)
         struct listener_list *listeners;
         struct taskstats *stats;
         struct sk_buff *rep_skb;
-        void *reply;
         size_t size;
         int is_thread_group;
 
@@ -486,17 +482,17 @@ void taskstats_exit(struct task_struct *tsk, int group_dead)
         if (list_empty(&listeners->list))
                 return;
 
-        rc = prepare_reply(NULL, TASKSTATS_CMD_NEW, &rep_skb, &reply, size);
+        rc = prepare_reply(NULL, TASKSTATS_CMD_NEW, &rep_skb, size);
         if (rc < 0)
                 return;
 
         stats = mk_reply(rep_skb, TASKSTATS_TYPE_PID, tsk->pid);
         if (!stats)
-                goto nla_err;
+                goto err;
 
         rc = fill_pid(tsk->pid, tsk, stats);
         if (rc < 0)
-                goto nla_err;
+                goto err;
 
         /*
          * Doesn't matter if tsk is the leader or the last group member leaving
@@ -506,16 +502,14 @@ void taskstats_exit(struct task_struct *tsk, int group_dead)
 
         stats = mk_reply(rep_skb, TASKSTATS_TYPE_TGID, tsk->tgid);
         if (!stats)
-                goto nla_err;
+                goto err;
 
         memcpy(stats, tsk->signal->stats, sizeof(*stats));
 
 send:
         send_cpu_listeners(rep_skb, listeners);
         return;
-
-nla_err:
-        genlmsg_cancel(rep_skb, reply);
+err:
         nlmsg_free(rep_skb);
 }