configs/hardening: Disable CONFIG_UBSAN_SIGNED_WRAP

kernel/configs/hardening.config turns on UBSAN for the bounds sanitizer, as that in combination with trapping can stop the exploitation of buffer overflows within the kernel. At the same time, hardening.config turns off every other UBSAN sanitizer because trapping means all UBSAN reports will be fatal and the problems brought up by other sanitizers generally do not have security implications. The signed integer overflow sanitizer was recently added back to the kernel and it is default on with just CONFIG_UBSAN=y, meaning that it gets enabled when merging hardening.config into another configuration. While this sanitizer does have security implications like the array bounds sanitizer, work to clean up enough instances to allow this to run in production environments is still ramping up, which means regular users and testers may be broken by these instances with CONFIG_UBSAN_TRAP=y. Disable CONFIG_UBSAN_SIGNED_WRAP in hardening.config to avoid this situation.

NCNathan Chancellor committed 2 years ago