Messages in this thread | | | Date | Fri, 31 Jul 2020 12:59:43 +0300 | From | Dan Carpenter <> | Subject | Re: [Linux-kernel-mentees] [PATCH net] rds: Prevent kernel-infoleak in rds_notify_queue_get() |
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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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