The linux 2.4 kernel before 2.4.19 assumes that the fninit instruction clears all registers, which could lead to an information leak on processors that do not clear all relevant SSE registers.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2002-1552
http://www.cs.helsinki.fi/linux/linux-kernel/2002-15/0760.html
http://www.cs.helsinki.fi/linux/linux-kernel/2002-15/0628.html
http://search.luky.org/linux-kernel.2002/msg24992.html
http://search.luky.org/linux-kernel.2002/msg24003.html
http://linux.bkbits.net:8080/linux-2.4/diffs/arch/i386/kernel/i387.c%401.6