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Fri, 11 Sep 2026 08:23:42 -0400 (EDT) Date: Fri, 11 Sep 2026 14:23:32 +0200 From: Greg KH To: Sasha Levin Cc: stable@vger.kernel.org, Bryam Vargas , Mikulas Patocka Subject: Re: [PATCH 7.2.y] dm-pcache: reject a kset that overruns its segment Message-ID: <2026091127-bubble-cupping-a7ee@gregkh> References: <2026090425-mutiny-unsent-560b@gregkh> <20260910001834.3752050-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260910001834.3752050-1-sashal@kernel.org> On Wed, Sep 09, 2026 at 08:18:34PM -0400, Sasha Levin wrote: > From: Bryam Vargas > > [ Upstream commit 7ac1f10f987a2ffae4aecf0e2ceca8f552b665cb ] > > 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 > Signed-off-by: Mikulas Patocka > [ backported missing writeback_errors support from the upstream dependency. ] > Signed-off-by: Sasha Levin > --- > drivers/md/dm-pcache/cache.h | 1 + > drivers/md/dm-pcache/cache_gc.c | 5 +++++ > drivers/md/dm-pcache/cache_key.c | 5 +++++ > drivers/md/dm-pcache/cache_writeback.c | 8 ++++++++ > 4 files changed, 19 insertions(+) > > diff --git a/drivers/md/dm-pcache/cache.h b/drivers/md/dm-pcache/cache.h > index afc112b79496a..93c1e699a3944 100644 > --- a/drivers/md/dm-pcache/cache.h > +++ b/drivers/md/dm-pcache/cache.h > @@ -180,6 +180,7 @@ struct pcache_cache { > u32 advance; > int ret; > } writeback_ctx; > + atomic_t writeback_errors; > > char gc_kset_onmedia_buf[PCACHE_KSET_ONMEDIA_SIZE_MAX]; > struct delayed_work gc_work; > diff --git a/drivers/md/dm-pcache/cache_gc.c b/drivers/md/dm-pcache/cache_gc.c > index 3088cfef951bc..99999a92c4e67 100644 > --- a/drivers/md/dm-pcache/cache_gc.c > +++ b/drivers/md/dm-pcache/cache_gc.c > @@ -134,6 +134,11 @@ 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 51dd1ccf4e2fd..93933651d2c96 100644 > --- a/drivers/md/dm-pcache/cache_key.c > +++ b/drivers/md/dm-pcache/cache_key.c > @@ -811,6 +811,11 @@ 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 3df8687e2382f..656e4d0489121 100644 > --- a/drivers/md/dm-pcache/cache_writeback.c > +++ b/drivers/md/dm-pcache/cache_writeback.c > @@ -229,6 +229,9 @@ void cache_writeback_fn(struct work_struct *work) > if (pcache_is_stopping(pcache)) > goto unlock; > > + if (atomic_read(&cache->writeback_errors)) > + goto unlock; > + > kset_onmedia = (struct pcache_cache_kset_onmedia *)cache->wb_kset_onmedia_buf; > > mutex_lock(&cache->dirty_tail_lock); > @@ -246,6 +249,11 @@ 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) { > delay = PCACHE_CACHE_WRITEBACK_INTERVAL; > -- > 2.53.0 > > Does not apply :(