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authorJoao Martins <joao.m.martins@oracle.com>2021-07-15 06:27:11 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2021-07-15 19:13:49 +0200
commitd08af0a59684e18a51aa4bfd24c658994ea3fc5b (patch)
tree20183f284e5c2d7f150ed5d359699491ad221af4 /mm/hugetlb.c
parenthfs: add lock nesting notation to hfs_find_init (diff)
downloadlinux-d08af0a59684e18a51aa4bfd24c658994ea3fc5b.tar.xz
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mm/hugetlb: fix refs calculation from unaligned @vaddr
Commit 82e5d378b0e47 ("mm/hugetlb: refactor subpage recording") refactored the count of subpages but missed an edge case when @vaddr is not aligned to PAGE_SIZE e.g. when close to vma->vm_end. It would then errousnly set @refs to 0 and record_subpages_vmas() wouldn't set the @pages array element to its value, consequently causing the reported null-deref by syzbot. Fix it by aligning down @vaddr by PAGE_SIZE in @refs calculation. Link: https://lkml.kernel.org/r/20210713152440.28650-1-joao.m.martins@oracle.com Fixes: 82e5d378b0e47 ("mm/hugetlb: refactor subpage recording") Reported-by: syzbot+a3fcd59df1b372066f5a@syzkaller.appspotmail.com Signed-off-by: Joao Martins <joao.m.martins@oracle.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/hugetlb.c')
-rw-r--r--mm/hugetlb.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 924553aa8f78..dfc940d5221d 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5440,8 +5440,9 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
continue;
}
- refs = min3(pages_per_huge_page(h) - pfn_offset,
- (vma->vm_end - vaddr) >> PAGE_SHIFT, remainder);
+ /* vaddr may not be aligned to PAGE_SIZE */
+ refs = min3(pages_per_huge_page(h) - pfn_offset, remainder,
+ (vma->vm_end - ALIGN_DOWN(vaddr, PAGE_SIZE)) >> PAGE_SHIFT);
if (pages || vmas)
record_subpages_vmas(mem_map_offset(page, pfn_offset),