From: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
Date: Thu, 4 Dec 2025 19:00:04 +0000 (+0000)
Subject: kasan: refactor pcpu kasan vmalloc unpoison
X-Git-Tag: v6.19-rc4~22^2~21
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6f13db031e27e88213381039032a9cc061578ea6;p=thirdparty%2Flinux.git

kasan: refactor pcpu kasan vmalloc unpoison

A KASAN tag mismatch, possibly causing a kernel panic, can be observed
on systems with a tag-based KASAN enabled and with multiple NUMA nodes.
It was reported on arm64 and reproduced on x86. 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 reusing __kasan_unpoison_vmalloc in a new helper in
preparation for the actual fix.

Link: https://lkml.kernel.org/r/eb61d93b907e262eefcaa130261a08bcb6c5ce51.1764874575.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>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Jiayuan Chen <jiayuan.chen@linux.dev>
Cc: Kees Cook <kees@kernel.org>
Cc: Marco Elver <elver@google.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: <stable@vger.kernel.org>	[6.1+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index df3d8567dde9..9c6ac4b62eb9 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -631,6 +631,16 @@ static __always_inline void kasan_poison_vmalloc(const void *start,
 		__kasan_poison_vmalloc(start, size);
 }
 
+void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms,
+				 kasan_vmalloc_flags_t flags);
+static __always_inline void
+kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms,
+			  kasan_vmalloc_flags_t flags)
+{
+	if (kasan_enabled())
+		__kasan_unpoison_vmap_areas(vms, nr_vms, flags);
+}
+
 #else /* CONFIG_KASAN_VMALLOC */
 
 static inline void kasan_populate_early_vm_area_shadow(void *start,
@@ -655,6 +665,11 @@ static inline void *kasan_unpoison_vmalloc(const void *start,
 static inline void kasan_poison_vmalloc(const void *start, unsigned long size)
 { }
 
+static __always_inline void
+kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms,
+			  kasan_vmalloc_flags_t flags)
+{ }
+
 #endif /* CONFIG_KASAN_VMALLOC */
 
 #if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) && \
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 1d27f1bd260b..b2b40c59ce18 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -28,6 +28,7 @@
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/bug.h>
+#include <linux/vmalloc.h>
 
 #include "kasan.h"
 #include "../slab.h"
@@ -575,3 +576,19 @@ bool __kasan_check_byte(const void *address, unsigned long ip)
 	}
 	return true;
 }
+
+#ifdef CONFIG_KASAN_VMALLOC
+void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms,
+				 kasan_vmalloc_flags_t flags)
+{
+	unsigned long size;
+	void *addr;
+	int area;
+
+	for (area = 0 ; area < nr_vms ; area++) {
+		size = vms[area]->size;
+		addr = vms[area]->addr;
+		vms[area]->addr = __kasan_unpoison_vmalloc(addr, size, flags);
+	}
+}
+#endif
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 94c0a9262a46..41dd01e8430c 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -5027,9 +5027,7 @@ 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, KASAN_VMALLOC_PROT_NORMAL);
 
 	kfree(vas);
 	return vms;