On Tue, Mar 05, 2019 at 11:36:35AM +0900, Masami Hiramatsu wrote:
> I think the better way to do this is allowing strncpy_from_user()
O
> if some conditions are match, like
>
> - strncpy_from_user() will be able to copy user memory with set_fs(USER_DS)
> - strncpy_from_user() can copy kernel memory with set_fs(KERNEL_DS)
> - strncpy_from_user() can access unsafe memory in IRQ context if
> pagefault is disabled.
>
> This is almost done, except for CONFIG_DEBUG_ATOMIC_SLEEP=y on x86.
>
> So, what about adding a condition to WARN_ON_IN_IRQ() like below
> instead of introducing user_access_ok() ?
>
> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
> index 780f2b42c8ef..ec0f0b74c9ab 100644
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -70,7 +70,7 @@ static inline bool __chk_range_not_ok(unsigned long addr,
> unsigned long size, un
> })
>
> #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
> -# define WARN_ON_IN_IRQ() WARN_ON_ONCE(!in_task())
> +# define WARN_ON_IN_IRQ() WARN_ON_ONCE(pagefault_disabled() &&
> !in_task())
That doesn't make any kind of sense to me; see faulthandler_disabled().
IOW. interrupt (and any atomic context really) won't take faults anyway.
I dislike that whole KERNEL_DS thing, but obviously that's not something
that's going away.
Would something like:
WARN_ON_ONCE(!(in_task || segment_eq(get_fs(), USER_DS)))
Work? Then we allow KERNEL_DS in task context, but for interrupt and
others require USER_DS.
