[PATCH 5.3 147/148] staging: erofs: detect potential multiref due to corrupted images

[Greg Kroah-Hartman]

From: Gao Xiang <gaoxian...@huawei.com>

commit e12a0ce2fa69798194f3a8628baf6edfbd5c548f upstream.

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: <sta...@vger.kernel.org> # 4.19+
Signed-off-by: Gao Xiang <gaoxian...@huawei.com>
Reviewed-by: Chao Yu <yuch...@huawei.com>
Link: https://lore.kernel.org/r/20190821140152.229648-1-gaoxian...@huawei.com
[ Gao Xiang: Since earlier kernels don't define EFSCORRUPTED,
             let's use EIO instead. ]
Signed-off-by: Gao Xiang <gaoxian...@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/staging/erofs/unzip_vle.c |   20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

--- a/drivers/staging/erofs/unzip_vle.c
+++ b/drivers/staging/erofs/unzip_vle.c
@@ -943,6 +943,7 @@ repeat:
        for (i = 0; i < nr_pages; ++i)
                pages[i] = NULL;
 
+       err = 0;
        z_erofs_pagevec_ctor_init(&ctor, Z_EROFS_NR_INLINE_PAGEVECS,
                                  work->pagevec, 0);
 
@@ -964,8 +965,17 @@ repeat:
                        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 (pages[pagenr]) {
+                       DBG_BUGON(1);
+                       SetPageError(pages[pagenr]);
+                       z_erofs_onlinepage_endio(pages[pagenr]);
+                       err = -EIO;
+               }
                pages[pagenr] = page;
        }
        sparsemem_pages = i;
@@ -975,7 +985,6 @@ repeat:
        overlapped = false;
        compressed_pages = grp->compressed_pages;
 
-       err = 0;
        for (i = 0; i < clusterpages; ++i) {
                unsigned int pagenr;
 
@@ -999,7 +1008,12 @@ repeat:
                        pagenr = z_erofs_onlinepage_index(page);
 
                        DBG_BUGON(pagenr >= nr_pages);
-                       DBG_BUGON(pages[pagenr]);
+                       if (pages[pagenr]) {
+                               DBG_BUGON(1);
+                               SetPageError(pages[pagenr]);
+                               z_erofs_onlinepage_endio(pages[pagenr]);
+                               err = -EIO;
+                       }
                        ++sparsemem_pages;
                        pages[pagenr] = page;