+ get_signal-dont-initialize-ksig-info-if-signal_group_exit-group_exec_task.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>]

The patch titled
     Subject: get_signal: don't initialize ksig->info if SIGNAL_GROUP_EXIT/group_exec_task
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     get_signal-dont-initialize-ksig-info-if-signal_group_exit-group_exec_task.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/get_signal-dont-initialize-ksig-info-if-signal_group_exit-group_exec_task.patch

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

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: get_signal: don't initialize ksig->info if SIGNAL_GROUP_EXIT/group_exec_task
Date: Mon, 26 Feb 2024 17:56:53 +0100

This initialization is incomplete and unnecessary, neither do_group_exit()
nor PF_USER_WORKER need ksig->info.

Link: https://lkml.kernel.org/r/20240226165653.GA20834@xxxxxxxxxx
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Peter Collingbourne <pcc@xxxxxxxxxx>
Cc: Wen Yang <wenyang.linux@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 kernel/signal.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/kernel/signal.c~get_signal-dont-initialize-ksig-info-if-signal_group_exit-group_exec_task
+++ a/kernel/signal.c
@@ -2727,12 +2727,15 @@ relock:
 		/* Has this task already been marked for death? */
 		if ((signal->flags & SIGNAL_GROUP_EXIT) ||
 		     signal->group_exec_task) {
-			clear_siginfo(&ksig->info);
-			ksig->info.si_signo = signr = SIGKILL;
+			signr = SIGKILL;
 			sigdelset(&current->pending.signal, SIGKILL);
 			trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
-				&sighand->action[SIGKILL - 1]);
+					     &sighand->action[SIGKILL-1]);
 			recalc_sigpending();
+			/*
+			 * implies do_group_exit() or return to PF_USER_WORKER,
+			 * no need to initialize ksig->info/etc.
+			 */
 			goto fatal;
 		}
 
_

Patches currently in -mm which might be from oleg@xxxxxxxxxx are

get_signal-dont-abuse-ksig-infosi_signo-and-ksig-sig.patch
get_signal-hide_si_addr_tag_bits-fix-the-usage-of-uninitialized-ksig.patch
get_signal-dont-initialize-ksig-info-if-signal_group_exit-group_exec_task.patch