[lkml]   [2021]   [Dec]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] hugetlbfs: Fix off-by-one error in hugetlb_vmdelete_list()
+Cc Andrew if he wants to take it though his tree.

On 12/28/21 15:42, Sean Christopherson wrote:
> Pass "end - 1" instead of "end" when walking the interval tree in
> hugetlb_vmdelete_list() to fix an inclusive vs. exclusive bug. The two
> callers that pass a non-zero "end" treat it as exclusive, whereas the
> interval tree iterator expects an inclusive "last". E.g. punching a hole
> in a file that precisely matches the size of a single hugepage, with a
> vma starting right on the boundary, will result in unmap_hugepage_range()
> being called twice, with the second call having start==end.
> The off-by-one error doesn't cause functional problems as
> __unmap_hugepage_range() turns into a massive nop due to short-circuiting
> its for-loop on "address < end". But, the mmu_notifier invocations to
> invalid_range_{start,end}() are passed a bogus zero-sized range, which
> may be unexpected behavior for secondary MMUs.
> The bug was exposed by commit ed922739c919 ("KVM: Use interval tree to do
> fast hva lookup in memslots"), currently queued in the KVM tree for 5.17,
> which added a WARN to detect ranges with start==end.
> Reported-by:
> Fixes: 1bfad99ab425 ("hugetlbfs: hugetlb_vmtruncate_list() needs to take a range to delete")
> Cc:
> Cc: Paolo Bonzini <>
> Signed-off-by: Sean Christopherson <>

Thanks Sean!

Reviewed-by: Mike Kravetz <>

> ---
> Not sure if this should go to stable@. It's mostly harmless, and likely
> nothing more than a minor performance blip when it's not harmless.

I am also unsure about the need to send to stable. It is possible automation
will pick it up and make that decision for us.
Mike Kravetz

 \ /
  Last update: 2021-12-29 04:53    [W:0.056 / U:0.140 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site