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 37F602D7380; Tue, 13 Oct 2026 12:26:02 +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=1791894363; cv=none; b=Yv/EztjeXxHtFCDT4vvMrk5Pi+wtfTdl23CQ1pX2B8EeaurYeezrLpMUL7M5F5Aasrvupz/dnv25smEUYtoFKvTrUQwAIcXG37iFG0CurY42U0TfmSPV//RR3ZKWHX3PDB9QatsJhMeJ+aFQtp1gjwyeFdxuX5H/a3R3KnQJtlQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791894363; c=relaxed/simple; bh=OkTC0loufrYv8lKq0OFNnbaRlHLNFqyxuLYiF3rihys=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MTEMJb5wNPviwV1cwNRF3DevyF2N2uc4WMah1ixQua8Od1BpWrC1OlDh7lUFPlR3b6/9L5pBTQYRHgG1CEit83knekjRHr4fh9HdY9r5lnuDzrGo9qzSTmOr8qpIEEH8u0DjPZpQBOLBFKnF7QHSUzCSArXwpX7fmUkwLbFVgCs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=MkGKhyyq; 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="MkGKhyyq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 938E21F000FF; Tue, 13 Oct 2026 12:26:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791894362; bh=xLJP6eyl11mrjc4zuPC28wzSr3UuS8KMfeuOIQWEEQQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=MkGKhyyq5Ed48wlVt8OjcMMmf031fc1MKOVkxqlN/Y4ElKXNRAsL0NEil+xvPQFHi Lgf+Lf3FiKpd6Ny6vdJgw1OB7aOnXvhfB0cCEuLWZ35BmMl+MRslTD3kenz67q7FTa 8rP48kefcNjBzgim9pIkNVkF1QuuWEnnxvyW3Yto= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Bryam Vargas , Mikulas Patocka , Sasha Levin Subject: [PATCH 6.18 491/621] dm-pcache: validate seg_id fields from persistent memory Date: Tue, 13 Oct 2026 13:38:06 +0200 Message-ID: <20261013112932.480356572@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261013112920.855194808@linuxfoundation.org> References: <20261013112920.855194808@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Bryam Vargas [ Upstream commit 90c990a68460d7b5720e5634cf650eccdf0f4098 ] cache_pos_decode(), cache_key_decode() and the last-kset branches of cache_replay(), the writeback worker and the GC worker take a cache segment id from the cache device metadata and index cache->segments[] with it without checking it against cache->n_segs. That metadata is only CRC-protected with a fixed public seed, so whoever supplies the cache device on a table load (CAP_SYS_ADMIN) controls the id; an out-of-range value forms a wild pcache_cache_segment pointer that is dereferenced and written through -- an out-of-bounds read and write driven by on-disk data. Add cache_seg_id_valid() and reject an out-of-range id at each decode site, failing the operation with -EIO instead of indexing past the array. Bound the id against the initialized-segment count (cache_info.n_segs) rather than the physical device total. A forged cache_info.n_segs below seg_num otherwise leaves segments[cache_info.n_segs..seg_num) as zeroed structs whose data pointer is NULL, so a forged id in that window would still be dereferenced. A later patch guarantees cache_info.n_segs <= seg_num, and a driver-created cache sets the two equal, so valid images are unaffected. 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 Signed-off-by: Sasha Levin --- drivers/md/dm-pcache/cache.c | 4 ++++ drivers/md/dm-pcache/cache.h | 14 ++++++++++++++ drivers/md/dm-pcache/cache_gc.c | 16 ++++++++++++++-- drivers/md/dm-pcache/cache_key.c | 11 +++++++++++ drivers/md/dm-pcache/cache_writeback.c | 20 ++++++++++++++++---- 5 files changed, 59 insertions(+), 6 deletions(-) diff --git a/drivers/md/dm-pcache/cache.c b/drivers/md/dm-pcache/cache.c index 8635fbf780aa0..013dfb171f0fc 100644 --- a/drivers/md/dm-pcache/cache.c +++ b/drivers/md/dm-pcache/cache.c @@ -118,6 +118,9 @@ int cache_pos_decode(struct pcache_cache *cache, if (!latest_addr) return -EIO; + if (!cache_seg_id_valid(cache, latest.cache_seg_id)) + return -EIO; + pos->cache_seg = &cache->segments[latest.cache_seg_id]; if (latest.seg_off >= pos->cache_seg->segment.data_size) @@ -158,6 +161,7 @@ static int cache_init(struct dm_pcache *pcache) cache->cache_dev = &pcache->cache_dev; cache->n_segs = cache_dev->seg_num; atomic_set(&cache->gc_errors, 0); + atomic_set(&cache->writeback_errors, 0); spin_lock_init(&cache->seg_map_lock); spin_lock_init(&cache->key_head_lock); diff --git a/drivers/md/dm-pcache/cache.h b/drivers/md/dm-pcache/cache.h index bf61a4a487bc0..8809ec5ae943c 100644 --- a/drivers/md/dm-pcache/cache.h +++ b/drivers/md/dm-pcache/cache.h @@ -421,6 +421,20 @@ static inline bool cache_seg_is_ctrl_seg(u32 cache_seg_id) return (cache_seg_id == 0); } +/** + * cache_seg_id_valid - Validate a cache segment id read from the cache device. + * @cache: Pointer to the pcache_cache structure. + * @cache_seg_id: Segment id decoded from on-media metadata. + * + * On-media segment ids are only protected by a CRC, which an attacker who can + * format the cache device computes over their chosen value. Reject any id that + * would index cache->segments[] out of bounds before it is dereferenced. + */ +static inline bool cache_seg_id_valid(struct pcache_cache *cache, u32 cache_seg_id) +{ + return cache_seg_id < cache->cache_info.n_segs; +} + /** * cache_key_cutfront - Cuts a specified length from the front of a cache key. * @key: Pointer to pcache_cache_key structure. diff --git a/drivers/md/dm-pcache/cache_gc.c b/drivers/md/dm-pcache/cache_gc.c index 99999a92c4e67..d551848912b45 100644 --- a/drivers/md/dm-pcache/cache_gc.c +++ b/drivers/md/dm-pcache/cache_gc.c @@ -74,11 +74,17 @@ static bool need_gc(struct pcache_cache *cache, struct pcache_cache_pos *dirty_t * @cache: Pointer to the pcache_cache structure. * @kset_onmedia: Pointer to the kset_onmedia structure for the last kset. */ -static void last_kset_gc(struct pcache_cache *cache, struct pcache_cache_kset_onmedia *kset_onmedia) +static int last_kset_gc(struct pcache_cache *cache, struct pcache_cache_kset_onmedia *kset_onmedia) { struct dm_pcache *pcache = CACHE_TO_PCACHE(cache); struct pcache_cache_segment *cur_seg, *next_seg; + if (!cache_seg_id_valid(cache, kset_onmedia->next_cache_seg_id)) { + pcache_dev_err(pcache, "invalid next_cache_seg_id %u in gc (n_segs %u)\n", + kset_onmedia->next_cache_seg_id, cache->n_segs); + return -EIO; + } + cur_seg = cache->key_tail.cache_seg; next_seg = &cache->segments[kset_onmedia->next_cache_seg_id]; @@ -94,6 +100,8 @@ static void last_kset_gc(struct pcache_cache *cache, struct pcache_cache_kset_on spin_lock(&cache->seg_map_lock); __clear_bit(cur_seg->cache_seg_id, cache->seg_map); spin_unlock(&cache->seg_map_lock); + + return 0; } void pcache_cache_gc_fn(struct work_struct *work) @@ -130,7 +138,11 @@ void pcache_cache_gc_fn(struct work_struct *work) if (dirty_tail.cache_seg == key_tail.cache_seg) break; - last_kset_gc(cache, kset_onmedia); + ret = last_kset_gc(cache, kset_onmedia); + if (ret) { + atomic_inc(&cache->gc_errors); + return; + } continue; } diff --git a/drivers/md/dm-pcache/cache_key.c b/drivers/md/dm-pcache/cache_key.c index c5a8ac02b216b..1526f5aa6a8db 100644 --- a/drivers/md/dm-pcache/cache_key.c +++ b/drivers/md/dm-pcache/cache_key.c @@ -103,6 +103,12 @@ int cache_key_decode(struct pcache_cache *cache, return -EIO; } + if (!cache_seg_id_valid(cache, key_onmedia->cache_seg_id)) { + pcache_dev_err(pcache, "invalid cache_seg_id %u in cache key (n_segs %u)\n", + key_onmedia->cache_seg_id, cache->n_segs); + return -EIO; + } + key->cache_pos.cache_seg = &cache->segments[key_onmedia->cache_seg_id]; key->cache_pos.seg_off = key_onmedia->cache_seg_off; @@ -810,6 +816,11 @@ int cache_replay(struct pcache_cache *cache) goto out; } + if (!cache_seg_id_valid(cache, kset_onmedia->next_cache_seg_id)) { + ret = -EIO; + goto out; + } + next_seg = &cache->segments[kset_onmedia->next_cache_seg_id]; pos->cache_seg = next_seg; diff --git a/drivers/md/dm-pcache/cache_writeback.c b/drivers/md/dm-pcache/cache_writeback.c index 656e4d0489121..c8a4c8110a581 100644 --- a/drivers/md/dm-pcache/cache_writeback.c +++ b/drivers/md/dm-pcache/cache_writeback.c @@ -196,12 +196,18 @@ static int cache_kset_insert_tree(struct pcache_cache *cache, struct pcache_cach return ret; } -static void last_kset_writeback(struct pcache_cache *cache, +static int last_kset_writeback(struct pcache_cache *cache, struct pcache_cache_kset_onmedia *last_kset_onmedia) { struct dm_pcache *pcache = CACHE_TO_PCACHE(cache); struct pcache_cache_segment *next_seg; + if (!cache_seg_id_valid(cache, last_kset_onmedia->next_cache_seg_id)) { + pcache_dev_err(pcache, "invalid next_cache_seg_id %u in writeback (n_segs %u)\n", + last_kset_onmedia->next_cache_seg_id, cache->n_segs); + return -EIO; + } + pcache_dev_debug(pcache, "last kset, next: %u\n", last_kset_onmedia->next_cache_seg_id); next_seg = &cache->segments[last_kset_onmedia->next_cache_seg_id]; @@ -211,6 +217,8 @@ static void last_kset_writeback(struct pcache_cache *cache, cache->dirty_tail.seg_off = 0; cache_encode_dirty_tail(cache); mutex_unlock(&cache->dirty_tail_lock); + + return 0; } void cache_writeback_fn(struct work_struct *work) @@ -244,7 +252,11 @@ void cache_writeback_fn(struct work_struct *work) } if (kset_onmedia->flags & PCACHE_KSET_FLAGS_LAST) { - last_kset_writeback(cache, kset_onmedia); + ret = last_kset_writeback(cache, kset_onmedia); + if (ret) { + atomic_inc(&cache->writeback_errors); + goto unlock; + } delay = 0; goto queue_work; } @@ -256,8 +268,8 @@ void cache_writeback_fn(struct work_struct *work) ret = cache_kset_insert_tree(cache, kset_onmedia); if (ret) { - delay = PCACHE_CACHE_WRITEBACK_INTERVAL; - goto queue_work; + atomic_inc(&cache->writeback_errors); + goto unlock; } cache_wb_tree_writeback(cache, get_kset_onmedia_size(kset_onmedia)); -- 2.53.0