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Date: Fri, 31 Jul 2020 12:59:43 +0300 From: Dan Carpenter <dan.carpenter@...cle.com> To: Leon Romanovsky <leon@...nel.org> Cc: Peilin Ye <yepeilin.cs@...il.com>, Santosh Shilimkar <santosh.shilimkar@...cle.com>, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman <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() 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. regards, dan carpenter
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