[PATCH 4.4 12/16] arm64: futex.h: Add missing PAN toggling

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: James Morse <james.morse@xxxxxxx>

commit 811d61e384e24759372bb3f01772f3744b0a8327 upstream.

futex.h's futex_atomic_cmpxchg_inatomic() does not use the
__futex_atomic_op() macro and needs its own PAN toggling. This was missed
when the feature was implemented.

Fixes: 338d4f49d6f ("arm64: kernel: Add support for Privileged Access Never")
Signed-off-by: James Morse <james.morse@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Cc: Mian Yousaf Kaukab <yousaf.kaukab@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/arm64/include/asm/futex.h |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/arm64/include/asm/futex.h
+++ b/arch/arm64/include/asm/futex.h
@@ -121,6 +121,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval,
 		return -EFAULT;
 
 	asm volatile("// futex_atomic_cmpxchg_inatomic\n"
+ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
 "	prfm	pstl1strm, %2\n"
 "1:	ldxr	%w1, %2\n"
 "	sub	%w3, %w1, %w4\n"
@@ -137,6 +138,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval,
 "	.align	3\n"
 "	.quad	1b, 4b, 2b, 4b\n"
 "	.popsection\n"
+ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
 	: "+r" (ret), "=&r" (val), "+Q" (*uaddr), "=&r" (tmp)
 	: "r" (oldval), "r" (newval), "Ir" (-EFAULT)
 	: "memory");