arm64: futex: Mask __user pointers prior to dereference

commit 91b2d3442f6a44dce875670d702af22737ad5eff upstream.

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>
Signed-off-by: Mark Rutland <mark.rutland@arm.com> [v4.9 backport]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h
index 20dcb19..4e5f36a 100644 (file)
--- a/arch/arm64/include/asm/futex.h
+++ b/arch/arm64/include/asm/futex.h
@@ -51,13 +51,14 @@
        : "memory")
 
 static inline int
-futex_atomic_op_inuser(unsigned int encoded_op, u32 __user *uaddr)
+futex_atomic_op_inuser(unsigned int encoded_op, u32 __user *_uaddr)
 {
        int op = (encoded_op >> 28) & 7;
        int cmp = (encoded_op >> 24) & 15;
        int oparg = (int)(encoded_op << 8) >> 20;
        int cmparg = (int)(encoded_op << 20) >> 20;
        int oldval = 0, ret, tmp;
+       u32 __user *uaddr = __uaccess_mask_ptr(_uaddr);
 
        if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
                oparg = 1U << (oparg & 0x1f);
@@ -109,15 +110,17 @@ futex_atomic_op_inuser(unsigned int encoded_op, 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);
        asm volatile("// futex_atomic_cmpxchg_inatomic\n"
 ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
 "      prfm    pstl1strm, %2\n"