[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>

diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index b0aad99c4f8d117c805fb285251ef3947f5ed3f2..4c3476fa058d5627650779f0559dc17c3a7cb1b8 100644 (file)
--- 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);
 }