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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/futex.c b/kernel/futex.c
index 322b9a840da634f465db970bfbd0f0f59a7c168e..6419e24abf64126206aece8776ffd3381c553e27 100644 (file)
--- 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)) {