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 <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Darren Hart <[email protected]>
Cc: Linus Torvalds <[email protected]>
---
kernel/futex.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index 4205ce8b8a7a..56712560fb63 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1564,8 +1564,8 @@ 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)) {
--
2.15.0
