Messages in this thread | | | Subject | Re: [PATCH net] vhost: Use kzalloc() to allocate vhost_msg_node | From | Jason Wang <> | Date | Sat, 28 Apr 2018 10:23:18 +0800 |
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On 2018年04月28日 09:51, Kevin Easton wrote: > On Fri, Apr 27, 2018 at 09:07:56PM -0400, Kevin Easton wrote: >> On Fri, Apr 27, 2018 at 07:05:45PM +0300, Michael S. Tsirkin wrote: >>> On Fri, Apr 27, 2018 at 11:45:02AM -0400, Kevin Easton wrote: >>>> The struct vhost_msg within struct vhost_msg_node is copied to userspace, >>>> so it should be allocated with kzalloc() to ensure all structure padding >>>> is zeroed. >>>> >>>> Signed-off-by: Kevin Easton <kevin@guarana.org> >>>> Reported-by: syzbot+87cfa083e727a224754b@syzkaller.appspotmail.com >>> Does it help if a patch naming the padding is applied, >>> and then we init just the relevant field? >>> Just curious. >> No, I don't believe that is sufficient to fix the problem. > Scratch that, somehow I missed the "..and then we init just the > relevant field" part, sorry. > > There's still the padding after the vhost_iotlb_msg to consider. It's > named in the union but I don't think that's guaranteed to be initialised > when the iotlb member of the union is used to initialise things. > >> I didn't name the padding in my original patch because I wasn't sure >> if the padding actually exists on 32 bit architectures? > This might still be a conce
Yes.
print &((struct vhost_msg *)0)->iotlb $3 = (struct vhost_iotlb_msg *) 0x4
> > At the end of the day, zeroing 96 bytes (the full size of vhost_msg_node) > is pretty quick. > > - Kevin
Right, and even if it may be used heavily in the data-path, zeroing is not the main delay in that path.
Thanks
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