Adding the KASAN maintainer so that we actuall have a chane of fixing this instead of a rant that just gets lost on the xfs list.. On Thu, Apr 18, 2024 at 03:04:24PM +1000, Dave Chinner wrote: > The only krealloc() in this path is: > > new = krealloc(ifp->if_data, new_size, > GFP_KERNEL | __GFP_NOLOCKDEP | __GFP_NOFAIL); > > And it explicitly uses __GFP_NOLOCKDEP to tell lockdep not to warn > about this allocation because of this false positive situation. > > Oh. I've seen this before. This is a KASAN bug, and I'm pretty sure > I've posted a patch to fix it a fair while back that nobody seemed > to care about enough to review or merge it. > > That is: kasan_save_stack() is doing a fixed GFP_KERNEL allocation > in an context where GFP_KERNEL allocations are known to generate > lockdep false positives. This occurs depsite the XFS and general > memory allocation code doing exactly the right thing to avoid the > lockdep false positives (i.e. using and obeying __GFP_NOLOCKDEP). > > The kasan code ends up in stack_depot_save_flags(), which does a > GFP_KERNEL allocation but filters out __GFP_NOLOCKDEP and does not > add it back. Hence kasan generates the false positive lockdep > warnings, not the code doing the original allocation. > > kasan and/or stack_depot_save_flags() needs fixing here. > > -Dave. > -- > Dave Chinner > david@xxxxxxxxxxxxx > ---end quoted text---
