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    SubjectRe: [PATCH 5/6] staging: erofs: detect potential multiref due to corrupted images
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    On 2019-8-19 18:34, Gao Xiang wrote:
    > As reported by erofs-utils fuzzer, currently, multiref
    > (ondisk deduplication) hasn't been supported for now,
    > we should forbid it properly.
    >
    > Fixes: 3883a79abd02 ("staging: erofs: introduce VLE decompression support")
    > Cc: <stable@vger.kernel.org> # 4.19+
    > Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
    > ---
    > drivers/staging/erofs/zdata.c | 16 ++++++++++++++--
    > 1 file changed, 14 insertions(+), 2 deletions(-)
    >
    > diff --git a/drivers/staging/erofs/zdata.c b/drivers/staging/erofs/zdata.c
    > index aae2f2b8353f..5b6fef5181af 100644
    > --- a/drivers/staging/erofs/zdata.c
    > +++ b/drivers/staging/erofs/zdata.c
    > @@ -816,8 +816,16 @@ static int z_erofs_decompress_pcluster(struct super_block *sb,
    > pagenr = z_erofs_onlinepage_index(page);
    >
    > DBG_BUGON(pagenr >= nr_pages);
    > - DBG_BUGON(pages[pagenr]);
    >
    > + /*
    > + * currently EROFS doesn't support multiref(dedup),
    > + * so here erroring out one multiref page.
    > + */
    > + if (unlikely(pages[pagenr])) {
    > + DBG_BUGON(1);
    > + SetPageError(pages[pagenr]);
    > + z_erofs_onlinepage_endio(pages[pagenr]);

    Should set err meanwhile?

    > + }
    > pages[pagenr] = page;
    > }
    > z_erofs_pagevec_ctor_exit(&ctor, true);
    > @@ -849,7 +857,11 @@ static int z_erofs_decompress_pcluster(struct super_block *sb,
    > pagenr = z_erofs_onlinepage_index(page);
    >
    > DBG_BUGON(pagenr >= nr_pages);
    > - DBG_BUGON(pages[pagenr]);
    > + if (unlikely(pages[pagenr])) {
    > + DBG_BUGON(1);
    > + SetPageError(pages[pagenr]);
    > + z_erofs_onlinepage_endio(pages[pagenr]);
    > + }
    > pages[pagenr] = page;
    >
    > overlapped = true;
    >

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