On Wed, May 13, 2020 at 11:52:10PM +0200, Pavel Machek wrote: > Hi! > > > From: Josh Poimboeuf <[email protected]> > > > > commit 98d0c8ebf77e0ba7c54a9ae05ea588f0e9e3f46e upstream. > > > > If the unwinder is called before the ORC data has been initialized, > > orc_find() returns NULL, and it tries to fall back to using frame > > pointers. This can cause some unexpected warnings during boot. > > > > Move the 'orc_init' check from orc_find() to __unwind_init(), so that it > > doesn't even try to unwind from an uninitialized state. > > > @@ -563,6 +560,9 @@ EXPORT_SYMBOL_GPL(unwind_next_frame); > > void __unwind_start(struct unwind_state *state, struct task_struct *task, > > struct pt_regs *regs, unsigned long *first_frame) > > { > > + if (!orc_init) > > + goto done; > > + > > memset(state, 0, sizeof(*state)); > > state->task = task; > > > > As this returns the *state to the caller, should the "goto done" move > below the memset? Otherwise we are returning partialy-initialized > struct, which is ... weird.
Yeah, it is a little weird. In most cases it should be fine, but there is an edge case where if there's a corrupt ORC table and this returns early, 'arch_stack_walk_reliable() -> unwind_error()' could check an uninitialized value. Also the __unwind_start() error handling needs to set that error bit anyway, in its error cases. I'll fix it up. -- Josh
