On Fri, 25 Feb 2022 09:33:45 -0800 Kees Cook <keescook@xxxxxxxxxxxx> wrote: > Under CONFIG_HARDENED_USERCOPY=y, when exact stack frame boundary checking > is not available (i.e. everything except x86 with FRAME_POINTER), check > a stack object as being at least "current depth valid", in the sense > that any object within the stack region but not between start-of-stack > and current_stack_pointer should be considered unavailable (i.e. its > lifetime is from a call no longer present on the stack). > > Introduce ARCH_HAS_CURRENT_STACK_POINTER to track which architectures > have actually implemented the common global register alias. > > Additionally report usercopy bounds checking failures with an offset > from current_stack_pointer, which may assist with diagnosing failures. > > The LKDTM USERCOPY_STACK_FRAME_TO and USERCOPY_STACK_FRAME_FROM tests > (once slightly adjusted in a separate patch) will pass again with > this fixed. Again, what does this actually do? > Reported-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx> A link to that report would shed some light. But actually describing the user-visible impact right there in the changelog is preferable. It sounds like a selftest is newly failing, which makes it a userspace-visible regression, perhaps? If so, do we have a Fixes: and is a cc:stable warranted?
