linux-kernel - Re: [Linux-kernel-mentees] [PATCH net] rds: Prevent kernel-infoleak in rds_notify_queue

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Message-Id: <20200731.165421.653261887142519995.davem@davemloft.net>
Date:   Fri, 31 Jul 2020 16:54:21 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     yepeilin.cs@...il.com
Cc:     santosh.shilimkar@...cle.com, kuba@...nel.org,
        dan.carpenter@...cle.com, arnd@...db.de,
        gregkh@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        rds-devel@....oracle.com, linux-kernel@...r.kernel.org
Subject: Re: [Linux-kernel-mentees] [PATCH net] rds: Prevent
 kernel-infoleak in rds_notify_queue_get()

From: Peilin Ye <yepeilin.cs@...il.com>
Date: Thu, 30 Jul 2020 15:20:26 -0400

> 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.
> 
> Cc: stable@...r.kernel.org
> Fixes: f037590fff30 ("rds: fix a leak of kernel memory")
> Fixes: bdbe6fbc6a2f ("RDS: recv.c")
> Suggested-by: Dan Carpenter <dan.carpenter@...cle.com>
> Signed-off-by: Peilin Ye <yepeilin.cs@...il.com>

Applied and queued up for -stable, thanks.

I saw a suggestion to use __packed but that breaks UAPI and is definitely
not an option to solve this problem.