[PATCH kernel v3] powerpc/uaccess: Skip might_fault() when user access is enabled

[Michael Ellerman]

On Thu, 4 Feb 2021 23:16:12 +1100, Alexey Kardashevskiy wrote:
> The amount of code executed with enabled user space access (unlocked KUAP)
> should be minimal. However with CONFIG_PROVE_LOCKING or
> CONFIG_DEBUG_ATOMIC_SLEEP enabled, might_fault() may end up replaying
> interrupts which in turn may access the user space and forget to restore
> the KUAP state.
> 
> The problem places are:
> 1. strncpy_from_user (and similar) which unlock KUAP and call
> unsafe_get_user -> __get_user_allowed -> __get_user_nocheck()
> with do_allow=false to skip KUAP as the caller took care of it.
> 2. __put_user_nocheck_goto() which is called with unlocked KUAP.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/uaccess: Avoid might_fault() when user access is enabled
      https://git.kernel.org/powerpc/c/7d506ca97b665b95e698a53697dad99fae813c1a

cheers