[PATCH] m68k: cmpxchg: Dereference matching size
From: Kees Cook
Date: Wed Feb 02 2022 - 17:53:33 EST
Similar to the recent arm64 fix[1], avoid overly wide casts in the cmpxchg
implementation. Avoid this warning under -Warray-bounds with GCC 11:
net/sched/cls_tcindex.c: In function 'tcindex_set_parms':
./arch/m68k/include/asm/cmpxchg.h:64:17: warning: array subscript 'volatile struct __xchg_dummy[0]' is partly outside array bounds of 'struct tcf_result[1]' [-Warray-bounds]
64 | __asm__ __volatile__
| ^~~~~~~
net/sched/cls_tcindex.c:338:27: note: while referencing 'cr'
338 | struct tcf_result cr = {};
| ^~
No binary output differences are seen from this change.
[1] commit 3364c6ce23c6 ("arm64: atomics: lse: Dereference matching size")
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
arch/m68k/include/asm/cmpxchg.h | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/arch/m68k/include/asm/cmpxchg.h b/arch/m68k/include/asm/cmpxchg.h
index e8ca4b0ccefa..6cf464cdab06 100644
--- a/arch/m68k/include/asm/cmpxchg.h
+++ b/arch/m68k/include/asm/cmpxchg.h
@@ -4,8 +4,7 @@
#include <linux/irqflags.h>
-struct __xchg_dummy { unsigned long a[100]; };
-#define __xg(x) ((volatile struct __xchg_dummy *)(x))
+#define __xg(type, x) ((volatile type *)(x))
extern unsigned long __invalid_xchg_size(unsigned long, volatile void *, int);
@@ -50,7 +49,7 @@ static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int siz
"1:\n\t"
"casb %0,%1,%2\n\t"
"jne 1b"
- : "=&d" (x) : "d" (x), "m" (*__xg(ptr)) : "memory");
+ : "=&d" (x) : "d" (x), "m" (*__xg(u8, ptr)) : "memory");
break;
case 2:
__asm__ __volatile__
@@ -58,7 +57,7 @@ static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int siz
"1:\n\t"
"casw %0,%1,%2\n\t"
"jne 1b"
- : "=&d" (x) : "d" (x), "m" (*__xg(ptr)) : "memory");
+ : "=&d" (x) : "d" (x), "m" (*__xg(u16, ptr)) : "memory");
break;
case 4:
__asm__ __volatile__
@@ -66,7 +65,7 @@ static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int siz
"1:\n\t"
"casl %0,%1,%2\n\t"
"jne 1b"
- : "=&d" (x) : "d" (x), "m" (*__xg(ptr)) : "memory");
+ : "=&d" (x) : "d" (x), "m" (*__xg(u32, ptr)) : "memory");
break;
default:
x = __invalid_xchg_size(x, ptr, size);
--
2.30.2