CVE-2021-46928

In the Linux kernel, the following vulnerability has been resolved: parisc:
Clear stale IIR value on instruction access rights trap When a trap 7
(Instruction access rights) occurs, this means the CPU couldn’t execute an
instruction due to missing execute permissions on the memory region. In
this case it seems the CPU didn’t even fetched the instruction from memory
and thus did not store it in the cr19 (IIR) register before calling the
trap handler. So, the trap handler will find some random old stale value in
cr19. This patch simply overwrites the stale IIR value with a constant
magic “bad food” value (0xbaadf00d), in the hope people don’t start to try
to understand the various random IIR values in trap 7 dumps.

Notes