[4/6] staging: erofs: avoid loop in submit chains
diff mbox series

Message ID 20190819103426.87579-5-gaoxiang25@huawei.com
State New
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Series
  • staging: erofs: first stage of corrupted compressed images
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Commit Message

Gao Xiang Aug. 19, 2019, 10:34 a.m. UTC
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.

Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
---
 drivers/staging/erofs/zdata.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

Comments

Chao Yu Aug. 19, 2019, 2:50 p.m. UTC | #1
On 2019-8-19 18:34, Gao Xiang wrote:
> 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.
> 
> Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,

Patch
diff mbox series

diff --git a/drivers/staging/erofs/zdata.c b/drivers/staging/erofs/zdata.c
index 23283c97fd3b..aae2f2b8353f 100644
--- a/drivers/staging/erofs/zdata.c
+++ b/drivers/staging/erofs/zdata.c
@@ -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))) {
@@ -381,6 +386,9 @@  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);
 	clt->pcl = pcl;
 	clt->cl = cl;
@@ -434,6 +442,9 @@  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;