On Wed, May 25, 2022 at 01:49:18PM +0100, Daniel Thompson wrote:
commit eadb2f47a3ced5c64b23b90fd2a3463f63726066 upstream.
KGDB and KDB allow read and write access to kernel memory, and thus should be restricted during lockdown. An attacker with access to a serial port (for example, via a hypervisor console, which some cloud vendors provide over the network) could trigger the debugger so it is important that the debugger respect the lockdown mode when/if it is triggered.
Fix this by integrating lockdown into kdb's existing permissions mechanism. Unfortunately kgdb does not have any permissions mechanism (although it certainly could be added later) so, for now, kgdb is simply and brutally disabled by immediately exiting the gdb stub without taking any action.
For lockdowns established early in the boot (e.g. the normal case) then this should be fine but on systems where kgdb has set breakpoints before the lockdown is enacted than "bad things" will happen.
CVE: CVE-2022-21499 Co-developed-by: Stephen Brennan stephen.s.brennan@oracle.com Signed-off-by: Stephen Brennan stephen.s.brennan@oracle.com Reviewed-by: Douglas Anderson dianders@chromium.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org
Notes: Original patch did not backport cleanly. This backport is fixed up, compile tested (on arm64) and side-by-side compared against the original.
Now queued up, thanks.
greg k-h