+ fork-zero-vmap-stack-using-clear_pages-instead-of-memset.patch added to mm-nonmm-unstable branch

+ fork-zero-vmap-stack-using-clear_pages-instead-of-memset.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: fork: zero vmap stack using clear_pages() instead of memset()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     fork-zero-vmap-stack-using-clear_pages-instead-of-memset.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fork-zero-vmap-stack-using-clear_pages-instead-of-memset.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: Linus Walleij <linusw@kernel.org>
Subject: fork: zero vmap stack using clear_pages() instead of memset()
Date: Tue, 24 Feb 2026 11:26:32 +0100

After the introduction of clear_pages() we exploit the fact that the
process vm_area is allocated in contiguous pages to just clear them all in
one swift operation.

Link: https://lkml.kernel.org/r/20260224-mm-fork-clear-pages-v1-1-184c65a72d49@kernel.org
Signed-off-by: Linus Walleij <linusw@kernel.org>
Suggested-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/linux-mm/dpnwsp7dl4535rd7qmszanw6u5an2p74uxfex4dh53frpb7pu3@2bnjjavjrepe/
Suggested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/20240311164638.2015063-7-pasha.tatashin@soleen.com
Cc: Ankur Arora <ankur.a.arora@oracle.com>
Cc: Ben Segall <bsegall@google.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/fork.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/fork.c~fork-zero-vmap-stack-using-clear_pages-instead-of-memset
+++ a/kernel/fork.c
@@ -350,7 +350,7 @@ static int alloc_thread_stack_node(struc
 		stack = kasan_reset_tag(vm_area->addr);
 
 		/* Clear stale pointers from reused stack. */
-		memset(stack, 0, THREAD_SIZE);
+		clear_pages(vm_area->addr, vm_area->nr_pages);
 
 		tsk->stack_vm_area = vm_area;
 		tsk->stack = stack;
_

Patches currently in -mm which might be from linusw@kernel.org are

fork-zero-vmap-stack-using-clear_pages-instead-of-memset.patch