From mboxrd@z Thu Jan 1 00:00:00 1970 From: Max Gurtovoy Subject: Re: [PATCH] IB/core: Fix different types mix in ib_device_cap_flags structure values Date: Wed, 1 Jun 2016 15:04:20 +0300 Message-ID: <574ECF44.3070003@mellanox.com> References: <1464602994-21226-1-git-send-email-maxg@mellanox.com> <08df9022-e575-da0d-c76d-a28185c9db2d@sandisk.com> <20160531171306.GA6618@obsidianresearch.com> <20160531173033.GC7477@leon.nu> <13f16fdf-e1d2-0baa-abe1-6423d2196b72@sandisk.com> <20160531181223.GE7477@leon.nu> <20160531182100.GC21834@obsidianresearch.com> <20160531185432.GF7477@leon.nu> <20160531193956.GD21834@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20160531193956.GD21834@obsidianresearch.com> Sender: stable-owner@vger.kernel.org To: Jason Gunthorpe , Leon Romanovsky Cc: Bart Van Assche , matanb@mellanox.com, sagi@grimberg.me, linux-rdma@vger.kernel.org, stable@vger.kernel.org List-Id: linux-rdma@vger.kernel.org > The four constants have different types and the types are not > necessarily what you'd expect (eg FOO_VALUE3 has been promoted to a > 64 bit signed long, FOO_VALUE1 has been demoted to an int) > > So the enum is safe, but having different types of the values is > certainly unexpected. > > I still think the actual bug is only 1<<31 I pointed out earlier: > > enum Foo > { > FOO_VALUE1 = 1, > FOO_VALUE2 = ((uint64_t)2) << 32, > FOO_VALUE3 = 1<<31, > }; > uint64_t res = FOO_VALUE1 | FOO_VALUE2 | FOO_VALUE3; > printf("%lx\n",res); > == > ffffffff80000001 > > Which is clearly wrong. This is because signed int becomes sign > extended when converted to uint64_t, corrupting the upper bits. > > Since adding the ULL's doesn't make the enum constants have uniform > type I would not bother with the churn. tested this with single casting to IB_DEVICE_ON_DEMAND_PAGING (1 << 31) to (1ULL << 31). works fine. I'll send another patch today. Thanks, Max. > > Jason >