From: "Håkon Bugge" <haakon.bugge@oracle.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>,
Leon Romanovsky <leon@kernel.org>,
Peilin Ye <yepeilin.cs@gmail.com>,
Santosh Shilimkar <santosh.shilimkar@oracle.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
linux-kernel-mentees@lists.linuxfoundation.org,
netdev@vger.kernel.org,
OFED mailing list <linux-rdma@vger.kernel.org>,
rds-devel@oss.oracle.com, linux-kernel@vger.kernel.org
Subject: Re: [Linux-kernel-mentees] [PATCH net] rds: Prevent kernel-infoleak in rds_notify_queue_get()
Date: Fri, 31 Jul 2020 14:03:06 +0200 [thread overview]
Message-ID: <866B1B5B-0156-4EED-9599-51BEF5661DA9@oracle.com> (raw)
In-Reply-To: <20200731115909.GA1649637@kroah.com>
> On 31 Jul 2020, at 13:59, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
>
> On Fri, Jul 31, 2020 at 01:14:09PM +0200, Håkon Bugge wrote:
>>
>>
>>> On 31 Jul 2020, at 11:59, Dan Carpenter <dan.carpenter@oracle.com> wrote:
>>>
>>> On Fri, Jul 31, 2020 at 07:53:01AM +0300, Leon Romanovsky wrote:
>>>> On Thu, Jul 30, 2020 at 03:20:26PM -0400, Peilin Ye wrote:
>>>>> rds_notify_queue_get() is potentially copying uninitialized kernel stack
>>>>> memory to userspace since the compiler may leave a 4-byte hole at the end
>>>>> of `cmsg`.
>>>>>
>>>>> In 2016 we tried to fix this issue by doing `= { 0 };` on `cmsg`, which
>>>>> unfortunately does not always initialize that 4-byte hole. Fix it by using
>>>>> memset() instead.
>>>>
>>>> Of course, this is the difference between "{ 0 }" and "{}" initializations.
>>>>
>>>
>>> No, there is no difference. Even struct assignments like:
>>>
>>> foo = *bar;
>>>
>>> can leave struct holes uninitialized. Depending on the compiler the
>>> assignment can be implemented as a memset() or as a series of struct
>>> member assignments.
>>
>> What about:
>>
>> struct rds_rdma_notify {
>> __u64 user_token;
>> __s32 status;
>> } __attribute__((packed));
>
> Why is this still a discussion at all?
>
> Try it and see, run pahole and see if there are holes in this structure
> (odds are no), you don't need us to say what is happening here...
An older posting had this:
$ pahole -C "rds_rdma_notify" net/rds/recv.o
struct rds_rdma_notify {
__u64 user_token; /* 0 8 */
__s32 status; /* 8 4 */
/* size: 16, cachelines: 1, members: 2 */
/* padding: 4 */
/* last cacheline: 16 bytes */
};
Thxs, Håkon
next prev parent reply other threads:[~2020-07-31 12:05 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-30 19:20 [Linux-kernel-mentees] [PATCH net] rds: Prevent kernel-infoleak in rds_notify_queue_get() Peilin Ye
2020-07-30 19:29 ` santosh.shilimkar
2020-07-31 4:53 ` Leon Romanovsky
2020-07-31 5:33 ` Greg Kroah-Hartman
2020-07-31 5:33 ` Greg Kroah-Hartman
[not found] ` <CAHp75Vdr2HC_ogNhBCxxGut9=Z6pQMFiA0w-268OQv+5unYOTg@mail.gmail.com>
2020-07-31 7:00 ` Leon Romanovsky
2020-07-31 7:05 ` Andy Shevchenko
2020-07-31 14:04 ` Jason Gunthorpe
2020-07-31 14:21 ` Greg Kroah-Hartman
2020-07-31 14:36 ` Jason Gunthorpe
2020-07-31 17:19 ` Greg Kroah-Hartman
2020-07-31 18:27 ` Jason Gunthorpe
2020-08-01 8:00 ` Dan Carpenter
2020-08-01 14:40 ` Jason Gunthorpe
2020-08-03 9:34 ` Dan Carpenter
2020-08-01 5:38 ` Leon Romanovsky
2020-08-02 22:10 ` Jason Gunthorpe
2020-08-02 22:23 ` Joe Perches
2020-08-02 22:28 ` Jason Gunthorpe
2020-08-02 22:45 ` Joe Perches
2020-08-03 4:58 ` Leon Romanovsky
2020-08-03 23:06 ` Jason Gunthorpe
2020-08-08 22:57 ` Jack Leadford
2020-08-09 7:04 ` Leon Romanovsky
2020-08-14 17:07 ` Jason Gunthorpe
2020-07-31 9:59 ` Dan Carpenter
2020-07-31 11:14 ` Håkon Bugge
2020-07-31 11:59 ` Greg Kroah-Hartman
2020-07-31 12:03 ` Håkon Bugge [this message]
2020-07-31 23:54 ` David Miller
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