| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2021-46928: parisc: Clear stale IIR value on instruction access rights trap |
| |
| Description |
| =========== |
| |
| 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. |
| |
| The Linux kernel CVE team has assigned CVE-2021-46928 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Fixed in 5.10.90 with commit d01e9ce1af6116f812491d3d3873d204f10ae0b8 |
| Fixed in 5.15.13 with commit e96373f0a5f484bc1e193f9951dcb3adf24bf3f7 |
| Fixed in 5.16 with commit 484730e5862f6b872dca13840bed40fd7c60fa26 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2021-46928 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| arch/parisc/kernel/traps.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/d01e9ce1af6116f812491d3d3873d204f10ae0b8 |
| https://git.kernel.org/stable/c/e96373f0a5f484bc1e193f9951dcb3adf24bf3f7 |
| https://git.kernel.org/stable/c/484730e5862f6b872dca13840bed40fd7c60fa26 |
