From: Leon Romanovsky <leon@kernel.org>
To: Peilin Ye <yepeilin.cs@gmail.com>
Cc: Santosh Shilimkar <santosh.shilimkar@oracle.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Dan Carpenter <dan.carpenter@oracle.com>,
Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel-mentees@lists.linuxfoundation.org,
netdev@vger.kernel.org, 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 07:53:01 +0300 [thread overview]
Message-ID: <20200731045301.GI75549@unreal> (raw)
In-Reply-To: <20200730192026.110246-1-yepeilin.cs@gmail.com>
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.
>
> Cc: stable@vger.kernel.org
> Fixes: f037590fff30 ("rds: fix a leak of kernel memory")
> Fixes: bdbe6fbc6a2f ("RDS: recv.c")
> Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
> ---
> Note: the "real" copy_to_user() happens in put_cmsg(), where
> `cmlen - sizeof(*cm)` equals to `sizeof(cmsg)`.
>
> Reference: https://lwn.net/Articles/417989/
>
> $ 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 */
> };
>
> net/rds/recv.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/rds/recv.c b/net/rds/recv.c
> index c8404971d5ab..aba4afe4dfed 100644
> --- a/net/rds/recv.c
> +++ b/net/rds/recv.c
> @@ -450,12 +450,13 @@ static int rds_still_queued(struct rds_sock *rs, struct rds_incoming *inc,
> int rds_notify_queue_get(struct rds_sock *rs, struct msghdr *msghdr)
> {
> struct rds_notifier *notifier;
> - struct rds_rdma_notify cmsg = { 0 }; /* fill holes with zero */
> + struct rds_rdma_notify cmsg;
> unsigned int count = 0, max_messages = ~0U;
> unsigned long flags;
> LIST_HEAD(copy);
> int err = 0;
>
> + memset(&cmsg, 0, sizeof(cmsg)); /* fill holes with zero */
It works, but the right solution is to drop 0 from cmsg initialization
and write "struct rds_rdma_notify cmsg = {};" without any memset.
Thanks
next prev parent reply other threads:[~2020-07-31 4:53 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 [this message]
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
2020-07-31 23:54 ` David Miller
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