[PATCH] powerpc/kasan/book3s_64: warn when running with hash MMU

[Michael Ellerman]

Christophe Leroy <christophe.leroy at csgroup.eu> writes:
> + KASAN list
>
> Le 06/10/2022 à 06:10, Michael Ellerman a écrit :
>> Nathan Lynch <nathanl at linux.ibm.com> writes:
>>> kasan is known to crash at boot on book3s_64 with non-radix MMU. As
>>> noted in commit 41b7a347bf14 ("powerpc: Book3S 64-bit outline-only
>>> KASAN support"):
>>>
>>>    A kernel with CONFIG_KASAN=y will crash during boot on a machine
>>>    using HPT translation because not all the entry points to the
>>>    generic KASAN code are protected with a call to kasan_arch_is_ready().
>> 
>> I guess I thought there was some plan to fix that.
>
> I was thinking the same.
>
> Do we have a list of the said entry points to the generic code that are 
> lacking a call to kasan_arch_is_ready() ?
>
> Typically, the BUG dump below shows that kasan_byte_accessible() is 
> lacking the check. It should be straight forward to add 
> kasan_arch_is_ready() check to kasan_byte_accessible(), shouldn't it ?

Yes :)

And one other spot, but the patch below boots OK for me. I'll leave it
running for a while just in case there's a path I've missed.

cheers


diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 69f583855c8b..5def0118f2cd 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -377,6 +377,9 @@ bool __kasan_slab_free(struct kmem_cache *cache, void *object,
 
 static inline bool ____kasan_kfree_large(void *ptr, unsigned long ip)
 {
+	if (!kasan_arch_is_ready())
+		return false;
+
 	if (ptr != page_address(virt_to_head_page(ptr))) {
 		kasan_report_invalid_free(ptr, ip, KASAN_REPORT_INVALID_FREE);
 		return true;
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 437fcc7e77cf..017d3c69e3b3 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -191,7 +191,12 @@ bool kasan_check_range(unsigned long addr, size_t size, bool write,
 
 bool kasan_byte_accessible(const void *addr)
 {
-	s8 shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr));
+	s8 shadow_byte;
+
+	if (!kasan_arch_is_ready())
+		return true;
+
+	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr));
 
 	return shadow_byte >= 0 && shadow_byte < KASAN_GRANULE_SIZE;
 }