I found that commit afb2d666d025 ("zsmalloc: use copy_page for full page
copy") caused a false-positive KMSAN warning.
[ 50.030627][ T2974] BUG: KMSAN: use-after-free in obj_malloc+0x6cc/0x7b0
[ 50.165956][ T2974] Uninit was stored to memory at:
[ 50.170819][ T2974] obj_malloc+0x70a/0x7b0
[ 50.328931][ T2974] Uninit was created at:
[ 50.341845][ T2974] free_unref_page_prepare+0x130/0xfc0
We need to use instrumented version when KMSAN is enabled.
Let arch/x86/include/asm/page_64.h implement copy_page() using memcpy()
like arch/x86/include/asm/page_32.h does.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/page_64.h | 9 +++++++++
1 file changed, 9 insertions(+)
Changes in v2:
Update explanation, for I misinterpreted source/destination direction.
diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h
index cc6b8e087192..f13bba3a9dab 100644
--- a/arch/x86/include/asm/page_64.h
+++ b/arch/x86/include/asm/page_64.h
@@ -58,7 +58,16 @@ static inline void clear_page(void *page)
: "cc", "memory", "rax", "rcx");
}
+#ifdef CONFIG_KMSAN
+/* Use of non-instrumented assembly version confuses KMSAN. */
+void *memcpy(void *to, const void *from, __kernel_size_t len);
+static inline void copy_page(void *to, void *from)
+{
+ memcpy(to, from, PAGE_SIZE);
+}
+#else
void copy_page(void *to, void *from);
+#endif
#ifdef CONFIG_X86_5LEVEL
/*
--
2.34.1
