This is a patch to fix a local root exploit revealed in
early February 2008.  To apply it to the 2.6.21.5 kernel,
do this:

cd /usr/src/linux-2.6.21.5
zcat splice.c.gz | patch -p1

You'll then be ready to build patched kernels from the
config files in the other kernel-* directories.  Copy
the config file to /usr/src/linux-2.6.21.5/.config,
run "make oldconfig", run "make bzImage", and then
copy the files into (for example) kernel-generic:

cd kernel-generic
cp -a /usr/src/linux-2.6.21.5/System.map \
      /usr/src/linux-2.6.21.5/.config \
      /usr/src/linux-2.6.21.5/arch/i386/boot/bzImage .
gzip -9 System.map
mv .config config

Then build the Slackware kernel package like this:
./kernel-generic.SlackBuild

Don't forget to run lilo again if you use that.