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

mainline inclusion
from mainline-v6.2-rc1
commit d6aba4c8
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6BE56
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.2-rc4&id=d6aba4c8e20d4d2bf65d589953f6d891c178f3a3

--------------------------------

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 ed922739 ("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: 1bfad99a ("hugetlbfs: hugetlb_vmtruncate_list() needs to take a range to delete")
Signed-off-by: NSean Christopherson <seanjc@google.com>
Reported-by: syzbot+4e697fe80a31aa7efe21@syzkaller.appspotmail.com
Reviewed-by: NMike Kravetz <mike.kravetz@oracle.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NLi Lingfeng <lilingfeng3@huawei.com>
Reviewed-by: NZhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: NZhang Yi <yi.zhang@huawei.com>
Signed-off-by: NJialin Zhang <zhangjialin11@huawei.com>
(cherry picked from commit 787b77fa)

fs/hugetlbfs/inode.c

@@ -472,10 +472,11 @@ 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;