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authorSean Christopherson <seanjc@google.com>2022-01-14 14:08:30 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2022-01-15 16:30:30 +0200
commitd6aba4c8e20d4d2bf65d589953f6d891c178f3a3 (patch)
treeefd29aea77b2caf2881bdb8cb79b1a233848af3c /fs/hugetlbfs
parentf530243a172d2ff03f88d0056f838928d6445c6d (diff)
hugetlbfs: fix off-by-one error in hugetlb_vmdelete_list()
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. Link: https://lkml.kernel.org/r/20211228234257.1926057-1-seanjc@google.com Fixes: 1bfad99ab425 ("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>
Diffstat (limited to 'fs/hugetlbfs')
-rw-r--r--fs/hugetlbfs/inode.c7
1 files changed, 4 insertions, 3 deletions
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 49d2e686be74..a7c6c7498be0 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -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;