* [PATCH v2 4/6] staging: erofs: avoid loop in submit chains
@ 2019-08-21 3:09 Gao Xiang
0 siblings, 0 replies; only message in thread
From: Gao Xiang @ 2019-08-21 3:09 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: Chao Yu, devel, Miao Xie, LKML, weidu.du, linux-fsdevel,
linux-erofs, Gao Xiang
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: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
---
Hi Greg,
It seems that you picked up [PATCH 4/6], could you replace it
with this v2? It seems that I missed a condition here, which
can be observed after a much longer fuzzing on corrupted
compressed images. Or you could just drop this [PATCH 4/6]
patch when you apply to staging-next since those patches are
independent.
Thanks you very much,
Gao Xiang
drivers/staging/erofs/zdata.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/drivers/staging/erofs/zdata.c b/drivers/staging/erofs/zdata.c
index 2d7aaf98f7de..5f8d3ac0e813 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))) {
@@ -379,7 +384,13 @@ 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;
@@ -432,6 +443,9 @@ 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;
--
2.17.1
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