[PATCH v2] ARM: kasan: Only map modules if CONFIG_KASAN_VMALLOC=n

[Alexander A Sverdlin]

From: Alexander Sverdlin <alexander.sverdlin at nokia.com>

In case CONFIG_KASAN_VMALLOC=y kasan_populate_vmalloc() allocates the
shadow pages dynamically. But even worse is that kasan_release_vmalloc()
releases them, which is not compatible with create_mapping() of
MODULES_VADDR..MODULES_END range:

BUG: Bad page state in process kworker/9:1  pfn:2068b
page:e5e06160 refcount:0 mapcount:0 mapping:00000000 index:0x0
flags: 0x1000(reserved)
raw: 00001000 e5e06164 e5e06164 00000000 00000000 00000000 ffffffff 00000000
page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
bad because of flags: 0x1000(reserved)
Modules linked in: ip_tables
CPU: 9 PID: 154 Comm: kworker/9:1 Not tainted 5.4.188-... #1
Hardware name: LSI Axxia AXM55XX
Workqueue: events do_free_init
unwind_backtrace
show_stack
dump_stack
bad_page
free_pcp_prepare
free_unref_page
kasan_depopulate_vmalloc_pte
__apply_to_page_range
apply_to_existing_page_range
kasan_release_vmalloc
__purge_vmap_area_lazy
_vm_unmap_aliases.part.0
__vunmap
do_free_init
process_one_work
worker_thread
kthread

Reviewed-by: Linus Walleij <linus.walleij at linaro.org>
Signed-off-by: Alexander Sverdlin <alexander.sverdlin at nokia.com>
---

Changelog:
v2:
* more verbose comment

 arch/arm/mm/kasan_init.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mm/kasan_init.c b/arch/arm/mm/kasan_init.c
index 29caee9..46d9f4a 100644
--- a/arch/arm/mm/kasan_init.c
+++ b/arch/arm/mm/kasan_init.c
@@ -268,12 +268,17 @@ void __init kasan_init(void)
 
 	/*
 	 * 1. The module global variables are in MODULES_VADDR ~ MODULES_END,
-	 *    so we need to map this area.
+	 *    so we need to map this area if CONFIG_KASAN_VMALLOC=n. With
+	 *    VMALLOC support KASAN will manage this region dynamically,
+	 *    refer to kasan_populate_vmalloc() and ARM's implementation of
+	 *    module_alloc().
 	 * 2. PKMAP_BASE ~ PKMAP_BASE+PMD_SIZE's shadow and MODULES_VADDR
 	 *    ~ MODULES_END's shadow is in the same PMD_SIZE, so we can't
 	 *    use kasan_populate_zero_shadow.
 	 */
-	create_mapping((void *)MODULES_VADDR, (void *)(PKMAP_BASE + PMD_SIZE));
+	if (!IS_ENABLED(CONFIG_KASAN_VMALLOC) && IS_ENABLED(CONFIG_MODULES))
+		create_mapping((void *)MODULES_VADDR, (void *)(MODULES_END));
+	create_mapping((void *)PKMAP_BASE, (void *)(PKMAP_BASE + PMD_SIZE));
 
 	/*
 	 * KAsan may reuse the contents of kasan_early_shadow_pte directly, so
-- 
2.10.2