seccomp: cap instruction limit and log buffer to reasonable sizes
seccomp: cap instruction limit and log buffer to reasonable sizes

No more than the current limit of 1 million instructions aka 8 mb and no more
than a 4096 byte log buffer.

Reported-by: Alban Crequy <cf48a9f1523ee9907dfdfe7340b4d0a5425749a7@gmail.com>
Signed-off-by: Christian Brauner <48455ab3070520a2d174545c7239d6d0fabd9a83@ubuntu.com>

lxc/lxd,stgraber/lxd,hallyn/lxd,atxwebs/lxd,lxc/lxd,lxc/lxd,stgraber/lxd,lxc/lxd,hallyn/lxd,Skarlso/lxd,stgraber/lxd,stgraber/lxd,atxwebs/lxd,lxc/lxd,Skarlso/lxd,hallyn/lxd,stgraber/lxd,Skarlso/lxd,hallyn/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,hallyn/lxd,stgraber/lxd,atxwebs/lxd,Skarlso/lxd,atxwebs/lxd