[merged mm-nonmm-stable] get_signal-hide_si_addr_tag_bits-fix-the-usage-of-uninitialized-ksig.patch removed from -mm tree

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

The quilt patch titled
     Subject: get_signal: hide_si_addr_tag_bits: fix the usage of uninitialized ksig
has been removed from the -mm tree.  Its filename was
     get_signal-hide_si_addr_tag_bits-fix-the-usage-of-uninitialized-ksig.patch

This patch was dropped because it was merged into the mm-nonmm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Oleg Nesterov <oleg@redhat.com>
Subject: get_signal: hide_si_addr_tag_bits: fix the usage of uninitialized ksig
Date: Mon, 26 Feb 2024 17:56:50 +0100

ksig->ka and ksig->info are not initialized if get_signal() returns 0 or
if the caller is PF_USER_WORKER.

Check signr != 0 before SA_EXPOSE_TAGBITS and move the "out" label down.

The latter means that ksig->sig won't be initialized if a PF_USER_WORKER
thread gets a fatal signal but this is fine, PF_USER_WORKER's don't use
ksig. And there is nothing new, in this case ksig->ka and ksig-info are
not initialized anyway. Add a comment.

Link: https://lkml.kernel.org/r/20240226165650.GA20829@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Wen Yang <wenyang.linux@foxmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/signal.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--- a/kernel/signal.c~get_signal-hide_si_addr_tag_bits-fix-the-usage-of-uninitialized-ksig
+++ a/kernel/signal.c
@@ -2881,8 +2881,9 @@ relock:
 
 		/*
 		 * PF_USER_WORKER threads will catch and exit on fatal signals
-		 * themselves. They have cleanup that must be performed, so
-		 * we cannot call do_exit() on their behalf.
+		 * themselves. They have cleanup that must be performed, so we
+		 * cannot call do_exit() on their behalf. Note that ksig won't
+		 * be properly initialized, PF_USER_WORKER's shouldn't use it.
 		 */
 		if (current->flags & PF_USER_WORKER)
 			goto out;
@@ -2894,12 +2895,12 @@ relock:
 		/* NOTREACHED */
 	}
 	spin_unlock_irq(&sighand->siglock);
-out:
+
 	ksig->sig = signr;
 
-	if (!(ksig->ka.sa.sa_flags & SA_EXPOSE_TAGBITS))
+	if (signr && !(ksig->ka.sa.sa_flags & SA_EXPOSE_TAGBITS))
 		hide_si_addr_tag_bits(ksig);
-
+out:
 	return signr > 0;
 }
 
_

Patches currently in -mm which might be from oleg@redhat.com are