Commit bfc4ccb1 authored by Gao Xiang's avatar Gao Xiang Committed by Greg Kroah-Hartman
Browse files

staging: erofs: avoid loop in submit chains 



As reported by erofs-utils fuzzer, 2 conditions
can happen in corrupted images, which can cause
unexpected behaviors.
 - access the same pcluster one more time;
 - access the tail end pcluster again, e.g.
            _ access again (will trigger tail merging)
           |
     1 2 3 1 2             ->   1 2 3 1
     |_ tail end of the chain    \___/ (unexpected behavior)
Let's detect and avoid them now.

Reviewed-by: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190821030908.40282-1-gaoxiang25@huawei.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2cb05d87

drivers/staging/erofs/zdata.c

+15 −1
Original line number Diff line number Diff line
@@ -132,7 +132,7 @@ enum z_erofs_collectmode { 
struct z_erofs_collector {

	struct z_erofs_pagevec_ctor vector;



	struct z_erofs_pcluster *pcl;

	struct z_erofs_pcluster *pcl, *tailpcl;

	struct z_erofs_collection *cl;

	struct page **compressedpages;

	z_erofs_next_pcluster_t owned_head;
@@ -353,6 +353,11 @@ static struct z_erofs_collection *cllookup(struct z_erofs_collector *clt, 
		return NULL;



	pcl = container_of(grp, struct z_erofs_pcluster, obj);

	if (clt->owned_head == &pcl->next || pcl == clt->tailpcl) {

		DBG_BUGON(1);

		erofs_workgroup_put(grp);

		return ERR_PTR(-EFSCORRUPTED);

	}



	cl = z_erofs_primarycollection(pcl);

	if (unlikely(cl->pageofs != (map->m_la & ~PAGE_MASK))) {
@@ -381,7 +386,13 @@ static struct z_erofs_collection *cllookup(struct z_erofs_collector *clt, 
		}

	}

	mutex_lock(&cl->lock);

	/* used to check tail merging loop due to corrupted images */

	if (clt->owned_head == Z_EROFS_PCLUSTER_TAIL)

		clt->tailpcl = pcl;

	clt->mode = try_to_claim_pcluster(pcl, &clt->owned_head);

	/* clean tailpcl if the current owned_head is Z_EROFS_PCLUSTER_TAIL */

	if (clt->owned_head == Z_EROFS_PCLUSTER_TAIL)

		clt->tailpcl = NULL;

	clt->pcl = pcl;

	clt->cl = cl;

	return cl;
@@ -434,6 +445,9 @@ static struct z_erofs_collection *clregister(struct z_erofs_collector *clt, 
		kmem_cache_free(pcluster_cachep, pcl);

		return ERR_PTR(-EAGAIN);

	}

	/* used to check tail merging loop due to corrupted images */

	if (clt->owned_head == Z_EROFS_PCLUSTER_TAIL)

		clt->tailpcl = pcl;

	clt->owned_head = &pcl->next;

	clt->pcl = pcl;

	clt->cl = cl;