From 3fd855b4bea10e62519bf0adf2bd5de98942e5a6 Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Thu, 30 Nov 2017 15:35:44 +0100 Subject: [PATCH] futex: futex_wake_op, fix sign_extend32 sign bits commit d70ef22892ed6c066e51e118b225923c9b74af34 upstream. sign_extend32 counts the sign bit parameter from 0, not from 1. So we have to use "11" for 12th bit, not "12". This mistake means we have not allowed negative op and cmp args since commit 30d6e0a4190d ("futex: Remove duplicated code and fix undefined behaviour") till now. Fixes: 30d6e0a4190d ("futex: Remove duplicated code and fix undefined behaviour") Signed-off-by: Jiri Slaby Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Darren Hart Signed-off-by: Linus Torvalds Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- kernel/futex.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index 322b9a840da63..6419e24abf641 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1725,8 +1725,8 @@ static int futex_atomic_op_inuser(unsigned int encoded_op, u32 __user *uaddr) { unsigned int op = (encoded_op & 0x70000000) >> 28; unsigned int cmp = (encoded_op & 0x0f000000) >> 24; - int oparg = sign_extend32((encoded_op & 0x00fff000) >> 12, 12); - int cmparg = sign_extend32(encoded_op & 0x00000fff, 12); + int oparg = sign_extend32((encoded_op & 0x00fff000) >> 12, 11); + int cmparg = sign_extend32(encoded_op & 0x00000fff, 11); int oldval, ret; if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28)) { -- 2.51.0