Re: [PATCH v7 1/4] syscalls: Restore address limit after a syscall

* Thomas Garnier [off-list ref] wrote:

quoted

quoted

+#ifdef CONFIG_ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE
+/*
+ * This function is called when an architecture specific implementation detected
+ * an invalid address limit. The generic user-mode state checker will finish on
+ * the appropriate BUG_ON.
+ */
+asmlinkage void address_limit_check_failed(void)
+{
+     verify_pre_usermode_state();
+     panic("address_limit_check_failed called with a valid user-mode state");

It's very unconstructive to unconditionally panic the system, just because some
kernel code leaked the address limit! Do a warn-once printout and kill the current
task (i.e. don't continue execution), but don't crash everything else!

The original change did not crash the kernel for this exact reason.
Through reviews, there was an overall agreement that the kernel should
not continue in this state.

Ok, I guess we can try that - but the panic message is still pretty misleading:

	panic("address_limit_check_failed called with a valid user-mode state");

... so it was called with a _valid_ user-mode state, and we crash due to something 
valid? Huh?

( Also, the style rule applies to kernel messages as well: function names should 
  be referred to as "function_name()". )

Thanks,

	Ingo