+ kasan-unpoison-pcpu-chunks-with-base-address-tag.patch added to mm-hotfixes-unstable branch

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

The patch titled
     Subject: kasan: unpoison pcpu chunks with base address tag
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     kasan-unpoison-pcpu-chunks-with-base-address-tag.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kasan-unpoison-pcpu-chunks-with-base-address-tag.patch

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

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------------------------------------------------------
From: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
Subject: kasan: unpoison pcpu chunks with base address tag
Date: Wed, 29 Oct 2025 19:05:49 +0000

The problem presented here is related to NUMA systems and tag-based KASAN
modes - software and hardware ones.  It can be explained in the following
points:

1. There can be more than one virtual memory chunk.

2. Chunk's base address has a tag.

3. The base address points at the first chunk and thus inherits the
   tag of the first chunk.

4. The subsequent chunks will be accessed with the tag from the first
   chunk.

5. Thus, the subsequent chunks need to have their tag set to match
   that of the first chunk.

Refactor code by moving it into a helper in preparation for the actual
fix.

Link: https://lkml.kernel.org/r/fbce40a59b0a22a5735cb6e9b95c5a45a34b23cb.1761763681.git.m.wieczorretman@pm.me
Fixes: 1d96320f8d53 ("kasan, vmalloc: add vmalloc tagging for SW_TAGS")
Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
Tested-by: Baoquan He <bhe@redhat.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Barry Song <baohua@kernel.org>
Cc: Bill Wendling <morbo@google.com>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Breno Leitao <leitao@debian.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: FUJITA Tomonori <fujita.tomonori@gmail.com>
Cc: Guilherme Giacomo Simoes <trintaeoitogc@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Jeremy Linton <jeremy.linton@arm.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: levi.yun <yeoreum.yun@arm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Marco Elver <elver@google.com>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Mostafa Saleh <smostafa@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Pankaj Gupta <pankaj.gupta@amd.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Samuel Holland <samuel.holland@sifive.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Huth <thuth@redhat.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Xin Li (Intel) <xin@zytor.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>	[6.1+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/kasan.h |   10 ++++++++++
 mm/kasan/tags.c       |   11 +++++++++++
 mm/vmalloc.c          |    4 +---
 3 files changed, 22 insertions(+), 3 deletions(-)

--- a/include/linux/kasan.h~kasan-unpoison-pcpu-chunks-with-base-address-tag
+++ a/include/linux/kasan.h
@@ -614,6 +614,13 @@ static __always_inline void kasan_poison
 		__kasan_poison_vmalloc(start, size);
 }
 
+void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms);
+static __always_inline void kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms)
+{
+	if (kasan_enabled())
+		__kasan_unpoison_vmap_areas(vms, nr_vms);
+}
+
 #else /* CONFIG_KASAN_VMALLOC */
 
 static inline void kasan_populate_early_vm_area_shadow(void *start,
@@ -638,6 +645,9 @@ static inline void *kasan_unpoison_vmall
 static inline void kasan_poison_vmalloc(const void *start, unsigned long size)
 { }
 
+static inline void kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms)
+{ }
+
 #endif /* CONFIG_KASAN_VMALLOC */
 
 #if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) && \
--- a/mm/kasan/tags.c~kasan-unpoison-pcpu-chunks-with-base-address-tag
+++ a/mm/kasan/tags.c
@@ -18,6 +18,7 @@
 #include <linux/static_key.h>
 #include <linux/string.h>
 #include <linux/types.h>
+#include <linux/vmalloc.h>
 
 #include "kasan.h"
 #include "../slab.h"
@@ -146,3 +147,13 @@ void __kasan_save_free_info(struct kmem_
 {
 	save_stack_info(cache, object, 0, true);
 }
+
+void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms)
+{
+	int area;
+
+	for (area = 0 ; area < nr_vms ; area++) {
+		kasan_poison(vms[area]->addr, vms[area]->size,
+			     arch_kasan_get_tag(vms[area]->addr), false);
+	}
+}
--- a/mm/vmalloc.c~kasan-unpoison-pcpu-chunks-with-base-address-tag
+++ a/mm/vmalloc.c
@@ -4870,9 +4870,7 @@ retry:
 	 * With hardware tag-based KASAN, marking is skipped for
 	 * non-VM_ALLOC mappings, see __kasan_unpoison_vmalloc().
 	 */
-	for (area = 0; area < nr_vms; area++)
-		vms[area]->addr = kasan_unpoison_vmalloc(vms[area]->addr,
-				vms[area]->size, KASAN_VMALLOC_PROT_NORMAL);
+	kasan_unpoison_vmap_areas(vms, nr_vms);
 
 	kfree(vas);
 	return vms;
_

Patches currently in -mm which might be from maciej.wieczor-retman@intel.com are

kasan-unpoison-pcpu-chunks-with-base-address-tag.patch
kasan-unpoison-vms-addresses-with-a-common-tag.patch