linux-kernel - [PATCH v2] arm64/mm: fix variable 'tag' set but not used

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <1564670825-4050-1-git-send-email-cai@lca.pw>
Date:   Thu,  1 Aug 2019 10:47:05 -0400
From:   Qian Cai <cai@....pw>
To:     catalin.marinas@....com, will@...nel.org
Cc:     andreyknvl@...gle.com, aryabinin@...tuozzo.com, glider@...gle.com,
        dvyukov@...gle.com, linux-arm-kernel@...ts.infradead.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Qian Cai <cai@....pw>
Subject: [PATCH v2] arm64/mm: fix variable 'tag' set but not used

When CONFIG_KASAN_SW_TAGS=n, set_tag() is compiled away. GCC throws a
warning,

mm/kasan/common.c: In function '__kasan_kmalloc':
mm/kasan/common.c:464:5: warning: variable 'tag' set but not used
[-Wunused-but-set-variable]
  u8 tag = 0xff;
     ^~~

Fix it by making __tag_set() a static inline function the same as
arch_kasan_set_tag() in mm/kasan/kasan.h for consistency because there
is a macro in arch/arm64/include/asm/kasan.h,

 #define arch_kasan_set_tag(addr, tag) __tag_set(addr, tag)

However, when CONFIG_DEBUG_VIRTUAL=n and CONFIG_SPARSEMEM_VMEMMAP=y,
page_to_virt() will call __tag_set() with incorrect type of a
parameter, so fix that as well. Also, still let page_to_virt() return
"void *" instead of "const void *", so will not need to add a similar
cast in lowmem_page_address().

Signed-off-by: Qian Cai <cai@....pw>
---

v2: Fix compilation warnings of CONFIG_DEBUG_VIRTUAL=n spotted by Will.

 arch/arm64/include/asm/memory.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index b7ba75809751..fb04f10a78ab 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -210,7 +210,11 @@ static inline unsigned long kaslr_offset(void)
 #define __tag_reset(addr)	untagged_addr(addr)
 #define __tag_get(addr)		(__u8)((u64)(addr) >> 56)
 #else
-#define __tag_set(addr, tag)	(addr)
+static inline const void *__tag_set(const void *addr, u8 tag)
+{
+	return addr;
+}
+
 #define __tag_reset(addr)	(addr)
 #define __tag_get(addr)		0
 #endif
@@ -301,8 +305,8 @@ static inline void *phys_to_virt(phys_addr_t x)
 #define page_to_virt(page)	({					\
 	unsigned long __addr =						\
 		((__page_to_voff(page)) | PAGE_OFFSET);			\
-	unsigned long __addr_tag =					\
-		 __tag_set(__addr, page_kasan_tag(page));		\
+	const void *__addr_tag =					\
+		__tag_set((void *)__addr, page_kasan_tag(page));	\
 	((void *)__addr_tag);						\
 })
 
-- 
1.8.3.1