[PATCH v2 5/5] arm64: kernel: Don't toggle PAN on systems with UAO

Hi Catalin,

On 18/02/16 14:36, Catalin Marinas wrote:

On Fri, Feb 05, 2016 at 02:58:50PM +0000, James Morse wrote:

quoted

--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c

@@ -234,6 +234,9 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
 	}
 
 	if (permission_fault(esr) && (addr < USER_DS)) {
+		if (get_thread_info(regs->sp)->addr_limit == KERNEL_DS)
+			panic("Accessing user space memory with fs=KERNEL_DS");

We could simply use "get_fs() == KERNEL_DS" as we should call
do_page_fault() outside the current context.

shouldn't?

You're right, it will always be on the same stack, so get_fs() will give us the
right result. This fits better with getting rid of the new get_thread_info() in
patch 3.


Thanks,

James