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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>
Subject: [PATCH 4.15 057/202] [Variant 1/Spectre-v1] arm64: futex: Mask __user pointers prior to dereference
Date:   Thu, 15 Feb 2018 16:15:57 +0100
Message-Id: <20180215151716.256293611@linuxfoundation.org>
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4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Will Deacon <will.deacon@arm.com>


Commit 91b2d3442f6a 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/arm64/include/asm/futex.h |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- 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
 }
 
 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"