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 couldnt execute an instruction due to missing execute permissions on the memory region. In this case it seems the CPU didnt 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 dont start to try to understand the various random IIR values in trap 7 dumps.

Weakness

The product does not handle or incorrectly handles an exceptional condition.

Affected Software

References

• https://git.kernel.org/stable/c/484730e5862f6b872dca13840bed40fd7c60fa26
• https://git.kernel.org/stable/c/d01e9ce1af6116f812491d3d3873d204f10ae0b8
• https://git.kernel.org/stable/c/e96373f0a5f484bc1e193f9951dcb3adf24bf3f7
• https://git.kernel.org/stable/c/484730e5862f6b872dca13840bed40fd7c60fa26
• https://git.kernel.org/stable/c/d01e9ce1af6116f812491d3d3873d204f10ae0b8
• https://git.kernel.org/stable/c/e96373f0a5f484bc1e193f9951dcb3adf24bf3f7