MIPS: Compat: Use 32-bit wrapper for compat_sys_futex.

We can't trust userspace to pass signed-extend arguments.  Not correctly
sign-extended arguments to futex-wait result in architecturally undefined
operation of 32-bit arithmetic instructions.

For example, if 'val' is too big and bit-31 is 1, the caller may enter
endless loop at:

futex_wait_setup()
{
	...

	if (uval != val) {
		queue_unlock(q, *hb);
		ret = -EWOULDBLOCK;

	...
}

Signed-off-by: Yong Zhang <yong.zhang@windriver.com>
To: linux-mips@linux-mips.org
To: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/2714/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

3 files changed, 9 insertions, 2 deletions

diff --git a/arch/mips/kernel/linux32.c b/arch/mips/kernel/linux32.c
index 876a75cc376f..922a554cd108 100644
--- a/arch/mips/kernel/linux32.c
+++ b/arch/mips/kernel/linux32.c
@@ -349,3 +349,10 @@ SYSCALL_DEFINE6(32_fanotify_mark, int, fanotify_fd, unsigned int, flags,
         return sys_fanotify_mark(fanotify_fd, flags, merge_64(a3, a4),
                                  dfd, pathname);
 }
+
+SYSCALL_DEFINE6(32_futex, u32 __user *, uaddr, int, op, u32, val,
+                struct compat_timespec __user *, utime, u32 __user *, uaddr2,
+                u32, val3)
+{
+        return compat_sys_futex(uaddr, op, val, utime, uaddr2, val3);
+}
diff --git a/arch/mips/kernel/scall64-n32.S b/arch/mips/kernel/scall64-n32.S
index f9296e894e46..6de1f598346e 100644
--- a/arch/mips/kernel/scall64-n32.S
+++ b/arch/mips/kernel/scall64-n32.S
@@ -315,7 +315,7 @@ EXPORT(sysn32_call_table)
         PTR     sys_fremovexattr
         PTR     sys_tkill
         PTR     sys_ni_syscall
-        PTR     compat_sys_futex
+        PTR     sys_32_futex
         PTR     compat_sys_sched_setaffinity    /* 6195 */
         PTR     compat_sys_sched_getaffinity
         PTR     sys_cacheflush
diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
index 4d7c9827706f..1d813169e453 100644
--- a/arch/mips/kernel/scall64-o32.S
+++ b/arch/mips/kernel/scall64-o32.S
@@ -441,7 +441,7 @@ sys_call_table:
         PTR     sys_fremovexattr                /* 4235 */
         PTR     sys_tkill
         PTR     sys_sendfile64
-        PTR     compat_sys_futex
+        PTR     sys_32_futex
         PTR     compat_sys_sched_setaffinity
         PTR     compat_sys_sched_getaffinity    /* 4240 */
         PTR     compat_sys_io_setup