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 08D7337F306; Fri, 4 Sep 2026 06:01:58 +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=1788501719; cv=none; b=TEmJw1N4jAXsb2HIQzsD4BO3S5sJJjKMSgqo5ogVxlF3o1wwY0zAjRCo4Nqys2YVBPDbza+DLA8ANz2KxP3LPJJbcEhuHXgjuYB0L7wGERKW5n/ge1qtR4AKOMyeDZZGYeIbM+UTIBUaxD7M0FxjQxbuJxVPjSmFGORqrKLG4l8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788501719; c=relaxed/simple; bh=OQbN4eJYVe6LKSseU7S0GzVQAo6rN2kp2N2fGmZnUDU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=W91Idwiv9ntcjSf9KjCGW5mHU8vAegjyz9aseKJCCJfjpVIE9w4AH1qazmk8EyQjjQI/UKNjiAyHohM5WDxK9WTbBozqmg2eeztD4wmHcyQNO73wwKV5AyIV+M7P+swDLvgeSDFlcBK69TkHzfuuJxLjDIS+GCPb3t+MnUYeoZ0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TbSAeE77; 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="TbSAeE77" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 649281F00A3E; Fri, 4 Sep 2026 06:01:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788501717; bh=YVNL76MunLfggOo7mxrGlwHqoFReVdcw99yl03k96+g=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=TbSAeE77eikoudoOIvkpiD8HEJXCCmS2sncuhJkbIeRWsGsvAAuI9/il4umKeotEN HJ0a3g0LyAAG7gMsWErjegTyFU57KNivo23Cor1dVWDGBtRNiT39CgxqYxYY67eGws hpMFt9mdgIir45PFo9br3VA1jAR9TuUn1Yq2fzqs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Bryam Vargas , Mikulas Patocka Subject: [PATCH 6.18 508/552] dm-pcache: validate on-media seg_num against the cache device size Date: Fri, 4 Sep 2026 07:01:05 +0200 Message-ID: <20260904045802.160187190@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045747.813364717@linuxfoundation.org> References: <20260904045747.813364717@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 commit 62d92e45abe9e087370f9fc5d876b95673aced34 upstream. seg_num is read from the crc32c-only superblock, so whoever supplies the cache device on a table load (CAP_SYS_ADMIN) controls it. It sizes cache->segments[] and is the value every later on-media segment id is bounded against, yet it is never checked against the device. Because cache_dev->mapping is the direct map of the pmem, CACHE_DEV_SEGMENT() for a segment id past the device resolves to ordinary kernel memory beyond the mapping; a new-cache init reaching such an id has cache_seg_init() -> cache_dev_zero_range() memset() 12 KiB over that memory -- an out-of-bounds write into the kernel heap at table load. A zero seg_num makes the segment allocations ZERO_SIZE_PTR. Reject a seg_num that is zero, larger than the device can hold, or larger than PCACHE_CACHE_SEGS_MAX before it is used. 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: Greg Kroah-Hartman --- drivers/md/dm-pcache/cache_dev.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm-pcache/cache_dev.c b/drivers/md/dm-pcache/cache_dev.c index ece689e6ce59..f0259353ee39 100644 --- a/drivers/md/dm-pcache/cache_dev.c +++ b/drivers/md/dm-pcache/cache_dev.c @@ -242,6 +242,8 @@ int cache_dev_start(struct dm_pcache *pcache) struct pcache_cache_dev *cache_dev = &pcache->cache_dev; struct pcache_sb sb; bool format = false; + u32 seg_num; + u64 max_segs; int ret; mutex_init(&cache_dev->seg_lock); @@ -269,7 +271,25 @@ int cache_dev_start(struct dm_pcache *pcache) goto dax_release; cache_dev->sb_flags = le32_to_cpu(sb.flags); - ret = cache_dev_init(cache_dev, le32_to_cpu(sb.seg_num)); + + /* + * seg_num is read from the crc32c-only superblock, so whoever supplies + * the cache device controls it. It is the ceiling every later on-media + * segment id is validated against, so bound it against what the device + * physically holds before it is trusted, or a forged seg_num lets a + * segment id address past the DAX mapping. + */ + seg_num = le32_to_cpu(sb.seg_num); + max_segs = (bdev_nr_bytes(cache_dev->dm_dev->bdev) - PCACHE_SEGMENTS_OFF) / + PCACHE_SEG_SIZE; + if (seg_num == 0 || seg_num > max_segs || seg_num > PCACHE_CACHE_SEGS_MAX) { + pcache_dev_err(pcache, "invalid seg_num %u from cache device (device holds %llu, max %u)\n", + seg_num, max_segs, (u32)PCACHE_CACHE_SEGS_MAX); + ret = -EIO; + goto dax_release; + } + + ret = cache_dev_init(cache_dev, seg_num); if (ret) goto dax_release; -- 2.55.0