| Message ID | 20210714010232.mZYMDcaPP%akpm@linux-foundation.org |
|---|---|
| State | New |
| Headers | show |
| Series | + mm-hugetlb-fix-refs-calculation-from-unaligned-vaddr.patch added to -mm tree | expand |
--- a/mm/hugetlb.c~mm-hugetlb-fix-refs-calculation-from-unaligned-vaddr +++ a/mm/hugetlb.c @@ -5440,8 +5440,9 @@ long follow_hugetlb_page(struct mm_struc 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),
The patch titled Subject: mm/hugetlb: fix refs calculation from unaligned @vaddr has been added to the -mm tree. Its filename is mm-hugetlb-fix-refs-calculation-from-unaligned-vaddr.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-fix-refs-calculation-from-unaligned-vaddr.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-fix-refs-calculation-from-unaligned-vaddr.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Joao Martins <joao.m.martins@oracle.com> Subject: 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> --- mm/hugetlb.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)