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hugetlbfs: fix off-by-one error in hugetlb_vmdelete_list()

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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 ed922739c9 ("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.

Link: https://lkml.kernel.org/r/20211228234257.1926057-1-seanjc@google.com
Fixes: 1bfad99ab4 ("hugetlbfs: hugetlb_vmtruncate_list() needs to take a range to delete")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reported-by: syzbot+4e697fe80a31aa7efe21@syzkaller.appspotmail.com
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Sean Christopherson 2022-01-14 14:08:30 -08:00 committed by Linus Torvalds
parent f530243a17
commit d6aba4c8e2
1 changed files with 4 additions and 3 deletions
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7
fs/hugetlbfs/inode.c
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@ -409,10 +409,11 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end)
struct vm_area_struct *vma;
/*
* end == 0 indicates that the entire range after
* start should be unmapped.
* end == 0 indicates that the entire range after start should be
* unmapped. Note, end is exclusive, whereas the interval tree takes
* an inclusive "last".
*/
vma_interval_tree_foreach(vma, root, start, end ? end : ULONG_MAX) {
vma_interval_tree_foreach(vma, root, start, end ? end - 1 : ULONG_MAX) {
unsigned long v_offset;
unsigned long v_end;