Comment 8 for bug 1680224

The two autofs patches Mark has attached aren't yet available on kernel.org
but I will (eventually) commit them to the autofs repo. and upload them.
The change will be included in autofs-5.1.3.

The only difference between what will be upstream and what has been posted
will be a single line description added to the autofs CHANGELOG (since there
hopefully won't be any further changes needed) and a Signed-off-by line
in the description.

The first patch is not strictly needed but the use of alloca() can be
unreliable in stack overflow conditions as (I believe) it never returns
a failure. So since it was used in the area that needed to be changed
I thought it best to fix it as part of the change.

The patch descriptions hopefully provide enough information for others
to understand what the problem was and why the change fixes the problem.