futex: futex_wake_op, fix sign_extend32 sign bits

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>

diff --git a/kernel/futex.c b/kernel/futex.c
index 76ed5921117a24cc347fa3aa79f59c2ba378897f..57d0b3657e16b90268fa3396668bb62e6e54d287 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1582,8 +1582,8 @@ 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)) {