[PATCH v2 05/11] dm-pcache: reject a kset that overruns its segment

[Bryam Vargas via B4 Relay <devnull+hexlabsecurity.proton.me@kernel.org>]

From: Bryam Vargas <hexlabsecurity@proton.me>

cache_replay(), the writeback worker and the GC worker read a kset of
get_kset_onmedia_size() bytes and advance the position by it. A forged
key_num makes that size exceed the segment's remaining space, so the
advance walks past the segment and trips the cache_pos_advance() BUG_ON.

Reject a kset whose on-media size exceeds cache_seg_remain() before use.

Fixes: 1d57628ff95b ("dm-pcache: add persistent cache target in device-mapper")
Cc: stable@vger.kernel.org
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
---
 drivers/md/dm-pcache/cache_gc.c        | 5 +++++
 drivers/md/dm-pcache/cache_key.c       | 5 +++++
 drivers/md/dm-pcache/cache_writeback.c | 5 +++++
 3 files changed, 15 insertions(+)

diff --git a/drivers/md/dm-pcache/cache_gc.c b/drivers/md/dm-pcache/cache_gc.c
index 1ed513745023..c483c7a3afaf 100644
--- a/drivers/md/dm-pcache/cache_gc.c
+++ b/drivers/md/dm-pcache/cache_gc.c
@@ -146,6 +146,11 @@ void pcache_cache_gc_fn(struct work_struct *work)
 			continue;
 		}
 
+		if (get_kset_onmedia_size(kset_onmedia) > cache_seg_remain(&key_tail)) {
+			atomic_inc(&cache->gc_errors);
+			return;
+		}
+
 		for (i = 0; i < kset_onmedia->key_num; i++) {
 			struct pcache_cache_key key_tmp = { 0 };
 
diff --git a/drivers/md/dm-pcache/cache_key.c b/drivers/md/dm-pcache/cache_key.c
index f4459b2e1b3b..d00497f9e462 100644
--- a/drivers/md/dm-pcache/cache_key.c
+++ b/drivers/md/dm-pcache/cache_key.c
@@ -818,6 +818,11 @@ int cache_replay(struct pcache_cache *cache)
 		}
 
 		/* Replay the kset and check for errors. */
+		if (get_kset_onmedia_size(kset_onmedia) > cache_seg_remain(pos)) {
+			ret = -EIO;
+			goto out;
+		}
+
 		ret = kset_replay(cache, kset_onmedia);
 		if (ret)
 			goto out;
diff --git a/drivers/md/dm-pcache/cache_writeback.c b/drivers/md/dm-pcache/cache_writeback.c
index 34c34b448e04..7a85a9aed18e 100644
--- a/drivers/md/dm-pcache/cache_writeback.c
+++ b/drivers/md/dm-pcache/cache_writeback.c
@@ -261,6 +261,11 @@ void cache_writeback_fn(struct work_struct *work)
 		goto queue_work;
 	}
 
+	if (get_kset_onmedia_size(kset_onmedia) > cache_seg_remain(&dirty_tail)) {
+		atomic_inc(&cache->writeback_errors);
+		goto unlock;
+	}
+
 	ret = cache_kset_insert_tree(cache, kset_onmedia);
 	if (ret) {
 		atomic_inc(&cache->writeback_errors);

-- 
2.43.0