On Mon, 2014-12-22 at 21:14 +0200, Kirill A. Shutemov wrote: > Other thing: > > unmap_mapping_range() > i_mmap_lock_read(mapping); > unmap_mapping_range_tree() > unmap_mapping_range_vma() > zap_page_range_single() > unmap_single_vma() > untrack_pfn() > vma->vm_flags &= ~VM_PAT; > > It seems we modify ->vm_flags without mmap_sem taken, means we can corrupt > them. yep. Although one thing that wouldn't match this would be the mlock'd bad page when freeing in both of Sasha's previous reports, as we would need to have VM_PFNMAP when calling untrack_pfn(). > Sasha could you check if you hit untrack_pfn()? > > The problem probably was hidden by exclusive i_mmap_lock on > unmap_mapping_range(), but it's not exclusive anymore afrer Dave's > patchset. > > Konstantin, you've modified untrack_pfn() back in 2012 to change > ->vm_flags. Any coments? > > For now, I would propose to revert the commit and probably re-introduce it > after v3.19: > > From 14392c69fcfeeda34eb9f75d983dad32698cdd5c Mon Sep 17 00:00:00 2001 > From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> > Date: Mon, 22 Dec 2014 21:01:54 +0200 > Subject: [PATCH] Revert "mm/memory.c: share the i_mmap_rwsem" > > This reverts commit c8475d144abb1e62958cc5ec281d2a9e161c1946. > > There are several[1][2] of bug reports which points to this commit as potential > cause[3]. > > Let's revert it until we figure out what's going on. > > [1] https://lkml.org/lkml/2014/11/14/342 > [2] https://lkml.org/lkml/2014/12/22/213 > [3] https://lkml.org/lkml/2014/12/9/741 > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Reported-by: Sasha Levin <sasha.levin@xxxxxxxxxx> > Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx> I certainly have no problem with this. Furthermore we snuck this one in kinda last minute, so: Acked-by: Davidlohr Bueso <dave@xxxxxxxxxxxx> Thanks, Davidlohr -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>