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 ---

changelog from v1: - change err = -EFSCORRUPTED as well as Chao suggested; [ the difference between adding err or not to [PATCH 5/6] is just whether we error out the whole compressed cluster or partial of them (since some pages could be decompressed successfully), it's an undefined behavior for these corrupted compressed images... ]

Hi Chao, Could you kindly review it again? Thanks!

Hi Greg, This is [PATCH 5/6] of the original patchset, and I fix as what Chao suggested... But I'm not sure whether it should be merged right now, it is up to you. :)

Thanks, Gao Xiang

drivers/staging/erofs/zdata.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/erofs/zdata.c b/drivers/staging/erofs/zdata.c index 4d6faaab04f5..60d7c20db87d 100644 --- 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;