Re: [Patch] 2.6.10.rc1.bk6 /lib/kobject_uevent.c buffer issues

[Greg KH]

On Sun, Oct 31, 2004 at 05:11:12AM +0100, Kay Sievers wrote:
> On Sat, Oct 30, 2004 at 04:54:29AM +0200, Kay Sievers wrote:
> > On Sat, Oct 30, 2004 at 02:25:23AM +0200, Kay Sievers wrote:
> > > On Sat, Oct 30, 2004 at 02:00:45AM +0200, Kay Sievers wrote:
> > > > On Fri, Oct 29, 2004 at 06:13:19PM -0500, Greg KH wrote:
> > > > > On Fri, Oct 29, 2004 at 11:28:56PM +0200, Kay Sievers wrote:
> > > > > > > But there might still be a problem.  With this change, the sequence
> > > > > > > number is not sent out the kevent message.  Kay, do you think this is an
> > > > > > > issue?  I don't think we can get netlink messages out of order, right?
> > > > > > 
> > > > > > Right, especially not the events with the same DEVPATH, like "remove"
> > > > > > beating an "add". But I'm not sure if the number isn't useful. Whatever
> > > > > > we may do with the hotplug over netlink in the future, we will only have
> > > > > > /sbin/hotplug for the early boot and it may be nice to know, what events
> > > > > > we have already handled...
> > > > > > 
> > > > > > > I'll hold off on applying this patch until we figure this out...
> > > > > > 
> > > > > > How about just reserving 20 bytes for the number (u64 will never be
> > > > > > more than that), save the pointer to that field, and fill the number in
> > > > > > later?
> > > > > 
> > > > > Ah, something like this instead?  I like it, it's even smaller than the
> > > > > previous patch.  Compile tested only...
> > > > 
> > > > I like that. How about the following. It will keep the buffer clean from
> > > > random chars, cause the kevent does not have the vector and relies on
> > > > the '\0' to separate the strings from each other.
> > > > I've tested it. The netlink-hotplug message looks like this:
> > > > 
> > > > recv(3, "remove@/class/input/mouse2\0ACTION=remove\0DEVPATH=/class/input/mouse2\0SUBSYSTEM=input\0SEQNUM=961                 \0", 1024, 0) = 113
> > > 
> > > Hmm, these trailing spaces are just bad, sorry. I'll better pass the
> > > envp array over to send_uevent() and clean up the keys while copying
> > > the env values into the skb buffer. This will make the event payload
> > > more safe too. So your first version looks better.
> > 
> > How about this? We copy over key by key into the skb buffer and the
> > netlink message can get the envp array without depending on a single
> > continuous buffer.
> > 
> > The netlink message looks nice like this now:
> > 
> > recv(3, "
> >   add@/devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2:1.0\0
> >   HOME=/\0
> >   PATH=/sbin:/bin:/usr/sbin:/usr/bin\0
> >   ACTION=add\0
> >   DEVPATH=/devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2:1.0\0
> >   SUBSYSTEM=usb\0
> >   SEQNUM=991\0
> >   DEVICE=/proc/bus/usb/003/008\0
> >   PRODUCT=46d/c03e/2000\0
> >   TYPE=0/0/0\0
> >   INTERFACE=3/1/2\0
> > ", 1024, 0) = 268
> 
> Here is an improved version that uses skb_put() to fill the skb buffer,
> instead of trimming the buffer to the final size after we've copied over
> all keys.

Thanks, I've applied this version.  Hopefully I'll get it out to Linus
later today.

greg k-h
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