On Sat, 9 May 2020, Thomas Gleixner wrote: > Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> writes: > > On Sat, May 09, 2020 at 12:20:14AM -0700, syzbot wrote: > >> memtype_reserve failed: [mem 0xffffffffff000-0x00008fff], req write-back > >> WARNING: CPU: 1 PID: 7025 at arch/x86/mm/pat/memtype.c:589 memtype_reserve+0x69f/0x820 arch/x86/mm/pat/memtype.c:589 > > > > So should memtype_reserve() not do a WARN if given invalid parameters as > > it can be triggered by userspace requests? > > > > A normal "invalid request" debug line is probably all that is needed, > > right? > > I disagree. The callsite espcially if user space triggerable should not > attempt to ask for a reservation where start > end: > > >> memtype_reserve failed: [mem 0xffffffffff000-0x00008fff], req write-back > > The real question is which part of the call chain is responsible for > this. That needs to be fixed. What about all the other ways in which a reservation request could be invalid? The MM core already checks for these; what point is there in duplicating these checks in many places higher up the call chain? Alan Stern
