+ taskstats-set-version-in-tgid-exit-notifications.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: taskstats: set version in TGID exit notifications
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     taskstats-set-version-in-tgid-exit-notifications.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/taskstats-set-version-in-tgid-exit-notifications.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Yiyang Chen <cyyzero16@gmail.com>
Subject: taskstats: set version in TGID exit notifications
Date: Mon, 30 Mar 2026 03:00:40 +0800

delay accounting started populating taskstats records with a valid version
field via fill_pid() and fill_tgid().

Later, commit ad4ecbcba728 ("[PATCH] delay accounting taskstats interface
send tgid once") changed the TGID exit path to send the cached
signal->stats aggregate directly instead of building the outgoing record
through fill_tgid().  Unlike fill_tgid(), fill_tgid_exit() only
accumulates accounting data and never initializes stats->version.

As a result, TGID exit notifications can reach userspace with version == 0
even though PID exit notifications and TASKSTATS_CMD_GET replies carry a
valid taskstats version.

This is easy to reproduce with `tools/accounting/getdelays.c`.

I have a small follow-up patch for that tool which:

1. increases the receive buffer/message size so the pid+tgid
   combined exit notification is not dropped/truncated

2. prints `stats->version`.

With that patch, the reproducer is:

  Terminal 1:
    ./getdelays -d -v -l -m 0

  Terminal 2:
    taskset -c 0 python3 -c 'import threading,time; t=threading.Thread(target=time.sleep,args=(0.1,)); t.start(); t.join()'

That produces both PID and TGID exit notifications for the same
process.  The PID exit record reports a valid taskstats version, while
the TGID exit record reports `version 0`.


This patch (of 2):

Set stats->version = TASKSTATS_VERSION after copying the cached TGID
aggregate into the outgoing netlink payload so all taskstats records are
self-describing again.

Link: https://lkml.kernel.org/r/ba83d934e59edd431b693607de573eb9ca059309.1774810498.git.cyyzero16@gmail.com
Fixes: ad4ecbcba728 ("[PATCH] delay accounting taskstats interface send tgid once")
Signed-off-by: Yiyang Chen <cyyzero16@gmail.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Dr. Thomas Orgis <thomas.orgis@uni-hamburg.de>
Cc: Fan Yu <fan.yu9@zte.com.cn>
Cc: Wang Yaxin <wang.yaxin@zte.com.cn>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/taskstats.c |    1 +
 1 file changed, 1 insertion(+)

--- a/kernel/taskstats.c~taskstats-set-version-in-tgid-exit-notifications
+++ a/kernel/taskstats.c
@@ -649,6 +649,7 @@ void taskstats_exit(struct task_struct *
 		goto err;
 
 	memcpy(stats, tsk->signal->stats, sizeof(*stats));
+	stats->version = TASKSTATS_VERSION;
 
 send:
 	send_cpu_listeners(rep_skb, listeners);
_

Patches currently in -mm which might be from cyyzero16@gmail.com are

taskstats-set-version-in-tgid-exit-notifications.patch
tools-accounting-handle-truncated-taskstats-netlink-messages.patch