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 <jslaby@suse.cz>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <dvhart@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/futex.c b/kernel/futex.c
index 401d99a4e3cb40b1836a800424eb357c7fdb1f4d..c3ea6f2a6997085da3adcb67d07cae1a86a5ebd9 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1462,8 +1462,8 @@ 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)) {