From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7D93C3F8ED6 for ; Fri, 4 Sep 2026 04:40:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788496855; cv=none; b=mcHtSkxd2qdc7vHwUCFYhW9TUx+aVYutuuYKO2kxGg1ApX97GWQvh1xfSzEMyinsxCEP/jF8SJiLqpePeHryVNxH9vDxS5PVeXPy+ITSrnbxAVSiV0cXde+qZGeocbHT3yylbWMxZzgLubAhcXkmNzL9KnxKM5PlwHpdCG4vipo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788496855; c=relaxed/simple; bh=H+K6S8PlrseNdfi3cUFr7+2W6g8jas3R4a0nhaa4g54=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=CCF41xVW3uwljNxb4lom9y8D64L/KaKFYZ3C2hwx3hibY9chOjXvL1qcugmNlCjpf9C5zFZpin+nEH95iANY0Zm6oKqdZrk5DobghaKxteaoBAR4G7NpROtjc6AJQdFuj/eanSaEXJmnG3ge8J6vzhEZFLbajT6un3YE5CYvwcI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=UhPy8/Ez; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="UhPy8/Ez" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8B5851F00A3E; Fri, 4 Sep 2026 04:40:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788496854; bh=Iu1aujYTX4KWhl6kBry2K7HqR0xruxTKVXCP6bKIbFs=; h=Subject:To:Cc:From:Date; b=UhPy8/Ez4AUva8dFmEet6rFwCEGhzO5QToT2KZUDjB2B0BpJZ05FZ6OwFLMH9t1KM KSEdylcX8hOrE9hLZ1usLhDycCYW8T3set5EkuY9gHbnGL29ysr1UdnVo1oPWBTR+4 aIvAMByMKz8FzORPmRxIU0xJWnDsQ4oLSj+FR9is= Subject: FAILED: patch "[PATCH] dm-pcache: validate the persisted dirty_tail chain at load" failed to apply to 6.18-stable tree To: hexlabsecurity@proton.me,mpatocka@redhat.com Cc: From: Date: Fri, 04 Sep 2026 06:40:11 +0200 Message-ID: <2026090411-harsh-specks-0d82@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x 58d620ee9e01d4bdbceaf2ae1450d307a2a9d58b # git commit -s git send-email --to '' --in-reply-to '2026090411-harsh-specks-0d82@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 58d620ee9e01d4bdbceaf2ae1450d307a2a9d58b Mon Sep 17 00:00:00 2001 From: Bryam Vargas Date: Fri, 17 Jul 2026 06:27:03 -0500 Subject: [PATCH] dm-pcache: validate the persisted dirty_tail chain at load The writeback worker follows the persisted dirty_tail chain, which is decoded from the cache device independently of the key_tail chain that cache_replay() walks and bounds. A crafted image, whose on-media fields are authenticated only by a crc32c with a fixed seed, can aim dirty_tail at a chain of last ksets that never terminates, so cache_writeback_fn() re-arms itself with no delay forever. Walk the dirty_tail chain once at load with the same hop cap cache_replay() uses and fail the table load with -EIO if it does not reach an end within n_segs hops. 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 diff --git a/drivers/md/dm-pcache/cache.c b/drivers/md/dm-pcache/cache.c index a94eadb7affd..b0b3e21677de 100644 --- a/drivers/md/dm-pcache/cache.c +++ b/drivers/md/dm-pcache/cache.c @@ -202,6 +202,7 @@ static int cache_tail_init(struct pcache_cache *cache) { struct dm_pcache *pcache = CACHE_TO_PCACHE(cache); bool new_cache = !(cache->cache_info.flags & PCACHE_CACHE_FLAGS_INIT_DONE); + int ret; if (new_cache) { __set_bit(0, cache->seg_map); @@ -218,6 +219,12 @@ static int cache_tail_init(struct pcache_cache *cache) pcache_dev_err(pcache, "Corrupted key tail or dirty tail.\n"); return -EIO; } + + ret = cache_verify_dirty_tail(cache); + if (ret) { + pcache_dev_err(pcache, "dirty tail chain does not terminate (crafted cache image?)\n"); + return ret; + } } return 0; diff --git a/drivers/md/dm-pcache/cache.h b/drivers/md/dm-pcache/cache.h index d9e3e09f18e3..8809ec5ae943 100644 --- a/drivers/md/dm-pcache/cache.h +++ b/drivers/md/dm-pcache/cache.h @@ -666,6 +666,8 @@ static inline int cache_decode_dirty_tail(struct pcache_cache *cache) &cache->dirty_tail_index); } +int cache_verify_dirty_tail(struct pcache_cache *cache); + int pcache_cache_init(void); void pcache_cache_exit(void); #endif /* _PCACHE_CACHE_H */ diff --git a/drivers/md/dm-pcache/cache_key.c b/drivers/md/dm-pcache/cache_key.c index f3ce319037be..1caea11a61a3 100644 --- a/drivers/md/dm-pcache/cache_key.c +++ b/drivers/md/dm-pcache/cache_key.c @@ -858,6 +858,75 @@ int cache_replay(struct pcache_cache *cache) return ret; } +/* + * cache_verify_dirty_tail - reject a persisted dirty_tail whose last-kset + * chain does not terminate. + * + * dirty_tail is decoded independently of the key_tail chain cache_replay() + * walks, so replay's hop cap does not cover it. A crafted chain that loops + * back on itself makes the writeback worker re-arm forever; walk it once here + * with the same cap and fail the load if it does not end within n_segs hops. + */ +int cache_verify_dirty_tail(struct pcache_cache *cache) +{ + struct pcache_cache_pos pos; + struct pcache_cache_kset_onmedia *kset_onmedia; + u32 to_copy, last_hops = 0, count = 0; + int ret = 0; + + kset_onmedia = kzalloc(PCACHE_KSET_ONMEDIA_SIZE_MAX, GFP_KERNEL); + if (!kset_onmedia) + return -ENOMEM; + + cache_pos_copy(&pos, &cache->dirty_tail); + + while (true) { + to_copy = min(PCACHE_KSET_ONMEDIA_SIZE_MAX, cache_seg_remain(&pos)); + ret = copy_mc_to_kernel(kset_onmedia, cache_pos_addr(&pos), to_copy); + if (ret) { + ret = -EIO; + goto out; + } + + /* A missing, short or corrupt kset is the normal end of the chain. */ + if (!kset_onmedia_valid(kset_onmedia) || + kset_onmedia->crc != cache_kset_crc(kset_onmedia)) { + ret = 0; + goto out; + } + + if (kset_onmedia->flags & PCACHE_KSET_FLAGS_LAST) { + if (!cache_seg_id_valid(cache, kset_onmedia->next_cache_seg_id)) { + ret = -EIO; + goto out; + } + + if (++last_hops > cache->n_segs) { + ret = -EIO; + goto out; + } + + pos.cache_seg = &cache->segments[kset_onmedia->next_cache_seg_id]; + pos.seg_off = 0; + continue; + } + + if (get_kset_onmedia_size(kset_onmedia) > cache_seg_remain(&pos)) { + ret = -EIO; + goto out; + } + + cache_pos_advance(&pos, get_kset_onmedia_size(kset_onmedia)); + if (++count > 512) { + cond_resched(); + count = 0; + } + } +out: + kfree(kset_onmedia); + return ret; +} + int cache_tree_init(struct pcache_cache *cache, struct pcache_cache_tree *cache_tree, u32 n_subtrees) { int ret;