[PATCH v6 06/18] khwasan, arm64: untag virt address in __kimg_to_phys and _virt_addr_is_linear
From: dvyukov@google.com (Dmitry Vyukov)
Date: 2018-09-12 16:34:21
Also in:
linux-doc, linux-kbuild, linux-mm, lkml
On Wed, Aug 29, 2018 at 1:35 PM, Andrey Konovalov [off-list ref] wrote:
quoted hunk ↗ jump to hunk
__kimg_to_phys (which is used by virt_to_phys) and _virt_addr_is_linear (which is used by virt_addr_valid) assume that the top byte of the address is 0xff, which isn't always the case with KHWASAN enabled. The solution is to reset the tag in those macros. Signed-off-by: Andrey Konovalov <redacted> --- arch/arm64/include/asm/memory.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index f5e262ee76c1..f5e2953b7009 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h@@ -92,6 +92,13 @@ #define KASAN_THREAD_SHIFT 0 #endif +#ifdef CONFIG_KASAN_HW +#define KASAN_TAG_SHIFTED(tag) ((unsigned long)(tag) << 56) +#define KASAN_SET_TAG(addr, tag) (((addr) & ~KASAN_TAG_SHIFTED(0xff)) | \ + KASAN_TAG_SHIFTED(tag)) +#define KASAN_RESET_TAG(addr) KASAN_SET_TAG(addr, 0xff) +#endif +
Wouldn't it be better to #define KASAN_RESET_TAG(addr) addr when CONFIG_KASAN_HW is not enabled, and then not duplicate the macros below? That's what we do in kasan.h for all hooks. I see that a subsequent patch duplicates yet another macro in this file. While we could use: #define __kimg_to_phys(addr) (KASAN_RESET_TAG(addr) - kimage_voffset) with and without kasan. Duplicating them increases risk that somebody will change only the non-kasan version but forget kasan version.
quoted hunk ↗ jump to hunk
#define MIN_THREAD_SHIFT (14 + KASAN_THREAD_SHIFT) /*@@ -232,7 +239,12 @@ static inline unsigned long kaslr_offset(void) #define __is_lm_address(addr) (!!((addr) & BIT(VA_BITS - 1))) #define __lm_to_phys(addr) (((addr) & ~PAGE_OFFSET) + PHYS_OFFSET) + +#ifdef CONFIG_KASAN_HW +#define __kimg_to_phys(addr) (KASAN_RESET_TAG(addr) - kimage_voffset) +#else #define __kimg_to_phys(addr) ((addr) - kimage_voffset) +#endif #define __virt_to_phys_nodebug(x) ({ \ phys_addr_t __x = (phys_addr_t)(x); \@@ -308,7 +320,13 @@ static inline void *phys_to_virt(phys_addr_t x) #endif #endif +#ifdef CONFIG_KASAN_HW +#define _virt_addr_is_linear(kaddr) (KASAN_RESET_TAG((u64)(kaddr)) >= \ + PAGE_OFFSET) +#else #define _virt_addr_is_linear(kaddr) (((u64)(kaddr)) >= PAGE_OFFSET) +#endif + #define virt_addr_valid(kaddr) (_virt_addr_is_linear(kaddr) && \ _virt_addr_valid(kaddr)) --2.19.0.rc0.228.g281dcd1b4d0-goog