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 0C18D377A8E for ; Fri, 4 Sep 2026 04:34:50 +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=1788496492; cv=none; b=CMfREO71JDjHMzklbEf+1ELw6hr9pFwxGqn6/YqB9ljK1LICLRU7DPOkGtIiYhhZmj8mwoVYbZfoe8oZtXs94ZcAjhUJJIAThedO52zQy5IxzXnM7r5ow4MbyebGY4rWcBiQwleLh3no1n0jPtwtFitIK4B0N+iu4DrVI5Tuau4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788496492; c=relaxed/simple; bh=OTwptTvxYPTjQijucK6c731zCOcLn+f2DykpjNRRnx4=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=l85JPjP0kA9+0XdvifLwopgliZHG7mQL5d7UFnLxboxZZNtgJecGbVV3apq9lSFlEQM9qpoYE6YZlZVyeC+l5zsQzUb94P3br4ILG3mIVs1xh7yflcom60CiTwPVpZj47zKC0fLXIMHZA1vFL5Qt7VM+Iv1XJI40BwmBtWGhNfg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=kNI9r2+r; 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="kNI9r2+r" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 213111F00A3D; Fri, 4 Sep 2026 04:34:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788496490; bh=lIori5oedpOzdHwfV4DyiQ0r/HMIkzAMjbpyQnAH4vQ=; h=Subject:To:Cc:From:Date; b=kNI9r2+rzg5Sb/l3VUfYeLP6CV833uZ61xBo4qworWyOVc8ORnJlQ/V74YiixksCZ Agk3WOzR62r5IBqIhQmsppiymMEQ0HUZJZAkyf7da9mjUxvsg+DwK26SjaEMQU9Skm F6MUaGtvHJMEQsQ9q+i/wT7Os5lLW9uCdz+fOGxk= Subject: FAILED: patch "[PATCH] dm-pcache: validate seg_id fields from persistent memory" failed to apply to 6.18-stable tree To: hexlabsecurity@proton.me,mpatocka@redhat.com Cc: From: Date: Fri, 04 Sep 2026 06:34:37 +0200 Message-ID: <2026090437-wok-unstable-1b2e@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 90c990a68460d7b5720e5634cf650eccdf0f4098 # git commit -s git send-email --to '' --in-reply-to '2026090437-wok-unstable-1b2e@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 90c990a68460d7b5720e5634cf650eccdf0f4098 Mon Sep 17 00:00:00 2001 From: Bryam Vargas Date: Fri, 17 Jul 2026 06:26:54 -0500 Subject: [PATCH] dm-pcache: validate seg_id fields from persistent memory 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 diff --git a/drivers/md/dm-pcache/cache.c b/drivers/md/dm-pcache/cache.c index bb1ada31e483..e9d2b87174d7 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]; pos->seg_off = latest.seg_off; *seq = latest.header.seq; @@ -155,6 +158,7 @@ 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 27613b56be54..919736379b76 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; @@ -420,6 +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 94f8b276a021..02fa0ce03134 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 e068e878231b..8eec5238c5da 100644 --- a/drivers/md/dm-pcache/cache_key.c +++ b/drivers/md/dm-pcache/cache_key.c @@ -94,6 +94,12 @@ int cache_key_decode(struct pcache_cache *cache, key->off = key_onmedia->off; key->len = key_onmedia->len; + 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; @@ -789,6 +795,11 @@ int cache_replay(struct pcache_cache *cache) pcache_dev_debug(pcache, "last kset replay, next: %u\n", kset_onmedia->next_cache_seg_id); + 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 87a82b3fe836..7751468d5118 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) @@ -229,6 +237,9 @@ 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); @@ -241,15 +252,19 @@ 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; } 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));