Patch "xtensa: fix futex_atomic_cmpxchg_inatomic" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

xtensa: fix futex_atomic_cmpxchg_inatomic

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
xtensa-fix-futex_atomic_cmpxchg_inatomic.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Max Filippov <[email protected]>
Date: Fri, 5 Jan 2018 14:27:58 -0800
Subject: xtensa: fix futex_atomic_cmpxchg_inatomic

From: Max Filippov <[email protected]>

commit ca47480921587ae30417dd234a9f79af188e3666 upstream.

Return 0 if the operation was successful, not the userspace memory value. Check that userspace value equals passed oldval, not itself. Don't update *uval if the value wasn't read from userspace memory.

This fixes process hang due to infinite loop in futex_lock_pi. It also fixes a bunch of glibc tests nptl/tst-mutexpi*.

---
 arch/xtensa/include/asm/futex.h |   23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

@@ -109,7 +109,6 @@ futex_atomic_cmpxchg_inatomic(u32 *uval,
 			      u32 oldval, u32 newval)
 {
 	int ret = 0;
-	u32 prev;
 
 	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
 		return -EFAULT;

@@ -120,26 +119,24 @@ futex_atomic_cmpxchg_inatomic(u32 *uval,
 
 	__asm__ __volatile__ (
 	"	# futex_atomic_cmpxchg_inatomic\n"
-	"1:	l32i	%1, %3, 0\n"
-	"	mov	%0, %5\n"
-	"	wsr	%1, scompare1\n"
-	"2:	s32c1i	%0, %3, 0\n"
-	"3:\n"
+	"	wsr	%5, scompare1\n"
+	"1:	s32c1i	%1, %4, 0\n"
+	"	s32i	%1, %6, 0\n"
+	"2:\n"
 	"	.section .fixup,\"ax\"\n"
 	"	.align 4\n"
-	"4:	.long	3b\n"
-	"5:	l32r	%1, 4b\n"
-	"	movi	%0, %6\n"
+	"3:	.long	2b\n"
+	"4:	l32r	%1, 3b\n"
+	"	movi	%0, %7\n"
 	"	jx	%1\n"
 	"	.previous\n"
 	"	.section __ex_table,\"a\"\n"
-	"	.long 1b,5b,2b,5b\n"
+	"	.long 1b,4b\n"
 	"	.previous\n"
-	: "+r" (ret), "=&r" (prev), "+m" (*uaddr)
-	: "r" (uaddr), "r" (oldval), "r" (newval), "I" (-EFAULT)
+	: "+r" (ret), "+r" (newval), "+m" (*uaddr), "+m" (*uval)
+	: "r" (uaddr), "r" (oldval), "r" (uval), "I" (-EFAULT)
 	: "memory");
 
-	*uval = prev;
 	return ret;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/xtensa-fix-futex_atomic_cmpxchg_inatomic.patch