A kernel update has been released for Slackware Linux:

New kernel packages are available for Slackware 8.1, 9.0, 9.1, and -current to fix a denial of service security issue. Without a patch to asm-i386/i387.h, a local user can crash the machine.

More details about this issue may be found in the Common Vulnerabilities and Exposures (CVE) database:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0554

Here are the details from the Slackware 9.1 ChangeLog:
+--------------------------+
Tue Jun 15 02:11:41 PDT 2004
patches/packages/kernel-ide-2.4.26-i486-3.tgz: Patched local DoS
(CAN-2004-0554). Without this patch to asm-i386/i387.h a local user
can crash the kernel.
(* Security fix *)
patches/packages/kernel-source-2.4.26-noarch-2.tgz: Patched local DoS
(CAN-2004-0554). The new patch can be found here, too:
patches/source/kernel-source/CAN-2004-0554.i387.fnclex.diff.gz
(* Security fix *)
patches/kernels/*: Patched local DoS (CAN-2004-0554).
(* Security fix *)
+--------------------------+


Where to find the new packages:
+-----------------------------+

Updated packages for Slackware 8.1:
ftp://ftp.slackware.com/pub/slackware/slackware-8.1/patches/packages/kernel-ide-2.4.18-i386-6.tgz
ftp://ftp.slackware.com/pub/slackware/slackware-8.1/patches/packages/kernel-source-2.4.18-noarch-7.tgz
ftp://ftp.slackware.com/pub/slackware/slackware-8.1/patches/kernels/

Updated packages for Slackware 9.0:
ftp://ftp.slackware.com/pub/slackware/slackware-9.0/patches/packages/kernel-ide-2.4.21-i486-4.tgz
ftp://ftp.slackware.com/pub/slackware/slackware-9.0/patches/packages/kernel-source-2.4.21-noarch-4.tgz
ftp://ftp.slackware.com/pub/slackware/slackware-9.0/patches/kernels/

Updated packages for Slackware 9.1:
ftp://ftp.slackware.com/pub/slackware/slackware-9.1/patches/packages/kernel-ide-2.4.26-i486-3.tgz
ftp://ftp.slackware.com/pub/slackware/slackware-9.1/patches/packages/kernel-source-2.4.26-noarch-2.tgz
ftp://ftp.slackware.com/pub/slackware/slackware-9.1/patches/kernels/

Updated packages for Slackware -current:
ftp://ftp.slackware.com/pub/slackware/slackware-current/slackware/a/kernel-ide-2.4.26-i486-4.tgz
ftp://ftp.slackware.com/pub/slackware/slackware-current/slackware/d/kernel-headers-2.4.26-i386-3.tgz
ftp://ftp.slackware.com/pub/slackware/slackware-current/slackware/k/kernel-source-2.4.26-noarch-4.tgz
ftp://ftp.slackware.com/pub/slackware/slackware-current/kernels/
ftp://ftp.slackware.com/pub/slackware/slackware-current/testing/packages/linux-2.6.6/kernel-generic-2.6.6-i486-5.tgz
ftp://ftp.slackware.com/pub/slackware/slackware-current/testing/packages/linux-2.6.6/kernel-headers-2.6.6-i386-3.tgz
ftp://ftp.slackware.com/pub/slackware/slackware-current/testing/packages/linux-2.6.6/kernel-source-2.6.6-noarch-3.tgz

Just the patch for 2.4.x kernels:
ftp://ftp.slackware.com/pub/slackware/slackware-9.1/patches/source/kernel-source/CAN-2004-0554.i387.fnclex.diff.gz
77d9eb0640f07df4167aaa53e0b42e2e CAN-2004-0554.i387.fnclex.diff.gz

Just the patch for 2.6.x kernels:
ftp://ftp.slackware.com/pub/slackware/slackware-current/testing/source/linux-2.6.x/CAN-2004-0554.i387.fnclex.diff.gz
e453d64187eac2216bebf85d72449fcb CAN-2004-0554.i387.fnclex.diff.gz


MD5 signatures:
+-------------+

Slackware 8.1 packages:
8bbced2d1f09d033de89ae5957427a25 kernel-ide-2.4.18-i386-6.tgz
050aa2dd8d38f0ba3de2fca621eb13c9 kernel-source-2.4.18-noarch-7.tgz

Slackware 9.0 packages:
21dbafdcf32d84c22daddc349a719420 kernel-ide-2.4.21-i486-4.tgz
56ca0fbf5778283a1d9a76a278cb7cf5 kernel-source-2.4.21-noarch-4.tgz

Slackware 9.1 packages:
614b79763721126939569f235d4524d6 kernel-ide-2.4.26-i486-3.tgz
43681f735928641a2b5fc786604bca77 kernel-source-2.4.26-noarch-2.tgz

Slackware -current packages:
7a19720356937bcc0f360b8b158a1419 kernel-ide-2.4.26-i486-4.tgz
c0d2d8b2977d5c86d100fe02a8c2681b kernel-headers-2.4.26-i386-3.tgz
8fbb66feb2d108baa6af6a895fc7f49a kernel-source-2.4.26-noarch-4.tgz
91ccc5ff7a5be15afdee86a60c6b408d kernel-generic-2.6.6-i486-5.tgz
bdcb17009e79bb375dad7fecdd7e60ae kernel-headers-2.6.6-i386-3.tgz
ed7c1e42f537414db8cd4dda8e2e9077 kernel-source-2.6.6-noarch-3.tgz


Installation instructions:
+------------------------+

Use upgradepkg to install the new packages. After installing the kernel-ide package you will need to run lilo ('lilo' at a command prompt) or create a new system boot disk ('makebootdisk'), and reboot.

If desired, a kernel from the kernels/ directory may be used instead. For example, to use the kernel in kernels/scsi.s/, you would copy it to the boot directory like this:

cd kernels/scsi.s
cp bzImage /boot/vmlinuz-scsi.s-2.4.26

Create a symbolic link:
ln -sf /boot/vmlinuz-scsi.s-2.4.26 /boot/vmlinuz

Then, run 'lilo' or create a new system boot disk and reboot.