arm64: futex: Mask __user pointers prior to dereference

The arm64 futex code has some explicit dereferencing of user pointers
where performing atomic operations in response to a futex command. This
patch uses masking to limit any speculative futex operations to within
the user address space.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h
index 5bb2fd4674e7..07fe2479d310 100644
--- a/arch/arm64/include/asm/futex.h
+++ b/arch/arm64/include/asm/futex.h
@@ -48,9 +48,10 @@ do {									\
 } while (0)
 
 static inline int
-arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
+arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *_uaddr)
 {
         int oldval = 0, ret, tmp;
+        u32 __user *uaddr = __uaccess_mask_ptr(_uaddr);
 
         pagefault_disable();
 
@@ -88,15 +89,17 @@ arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
 }
 
 static inline int
-futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *_uaddr,
                               u32 oldval, u32 newval)
 {
         int ret = 0;
         u32 val, tmp;
+        u32 __user *uaddr;
 
-        if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
+        if (!access_ok(VERIFY_WRITE, _uaddr, sizeof(u32)))
                 return -EFAULT;
 
+        uaddr = __uaccess_mask_ptr(_uaddr);
         uaccess_enable();
         asm volatile("// futex_atomic_cmpxchg_inatomic\n"
 "       prfm    pstl1strm, %2\n"