staging: erofs: detect potential multiref due to corrupted images

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>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20190821140152.229648-1-gaoxiang25@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/erofs/zdata.c b/drivers/staging/erofs/zdata.c
index 4d6faaab04f54933d1f16a9ddb499f8e1d954038..60d7c20db87db549c08fc1cf754f49cccc8814e9 100644 (file)
--- a/drivers/staging/erofs/zdata.c
+++ b/drivers/staging/erofs/zdata.c
@@ -798,6 +798,7 @@ static int z_erofs_decompress_pcluster(struct super_block *sb,
        for (i = 0; i < nr_pages; ++i)
                pages[i] = NULL;
 
+       err = 0;
        z_erofs_pagevec_ctor_init(&ctor, Z_EROFS_NR_INLINE_PAGEVECS,
                                  cl->pagevec, 0);
 
@@ -819,8 +820,17 @@ 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]);
+                       err = -EFSCORRUPTED;
+               }
                pages[pagenr] = page;
        }
        z_erofs_pagevec_ctor_exit(&ctor, true);
@@ -828,7 +838,6 @@ static int z_erofs_decompress_pcluster(struct super_block *sb,
        overlapped = false;
        compressed_pages = pcl->compressed_pages;
 
-       err = 0;
        for (i = 0; i < clusterpages; ++i) {
                unsigned int pagenr;
 
@@ -852,7 +861,12 @@ 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]);
+                               err = -EFSCORRUPTED;
+                       }
                        pages[pagenr] = page;
 
                        overlapped = true;