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 50B06285CBA; Wed, 20 May 2026 18:32:52 +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=1779301973; cv=none; b=IooZ0AH0naLEzNynuzFO3y7tUw3Bf47O32he8ZNFQf1fQG8xZJAD5Ld55d+6Et1hHs1bRRJOql8DYrueTCnFvh+eqwftU4jny80Y04re/6Ky4ZmMDzYrD6Bjd6sq+x0Yev302FAyCiIQnmf2DdMzAFQKq2PBFyVELutDBEA06u0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779301973; c=relaxed/simple; bh=mYS4/5Oryq5oG8fJgFovj8Of4siLofh0s4Y8EKF4wSA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ueDylHCBo0fILJA5CoSrixVNleg1QQtw1VRAyz3+MWMNHRWPNqvfOBP4SgHat7F8P5Qlj53Bxpc9Ysa8/qZD+gMNxSeZ5RNwnDgu6HPAar/MlPEi8ja4Kxo1by2sgd8d8+OEaOLE5lGcI9t1lPexOXE/jz4xj6Ed48ATjJYDoWQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xlPBD6pG; 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="xlPBD6pG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B5DD21F000E9; Wed, 20 May 2026 18:32:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779301972; bh=KRPPlO1SVOeu/JzvBXyOIwfKtwq9PAM+9VwPSyvmwUw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=xlPBD6pGCdOOFyBTiZhPMEpf0PQZeVQezJFsJAjs+Hcu0KUkKGKXLWxvuCb2qqRUJ PMK+Fh747r/CUaA34Zu4hBn+eoIXwH5wHcAsoA4WS38jeupi9KWvo1g4c9an/I+XxW vnJSYYLUmTQr3L7FNhcmjGUEuAlBiAQZJNsqjmpM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ming-Hung Tsai , Mikulas Patocka , Sasha Levin Subject: [PATCH 6.6 091/508] dm cache: fix null-deref with concurrent writes in passthrough mode Date: Wed, 20 May 2026 18:18:34 +0200 Message-ID: <20260520162100.587631008@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260520162058.573354582@linuxfoundation.org> References: <20260520162058.573354582@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 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ming-Hung Tsai [ Upstream commit 7d1f98d668ee34c1d15bdc0420fdd062f24a27c0 ] In passthrough mode, when dm-cache starts to invalidate a cache entry and bio prison cell lock fails due to concurrent write to the same cached block, mg->cell remains NULL. The error path in invalidate_complete() attempts to unlock and free the cell unconditionally, causing a NULL pointer dereference: KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 0 UID: 0 PID: 134 Comm: fio Not tainted 6.19.0-rc7 #3 PREEMPT RIP: 0010:dm_cell_unlock_v2+0x3f/0x210 Call Trace: invalidate_complete+0xef/0x430 map_bio+0x130f/0x1a10 cache_map+0x320/0x6b0 __map_bio+0x458/0x510 dm_submit_bio+0x40e/0x16d0 __submit_bio+0x419/0x870 Reproduce steps: 1. Create a cache device dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 131072 linear /dev/sdc 8192" dmsetup create corig --table "0 262144 linear /dev/sdc 262144" dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct dmsetup create cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" 2. Promote the first data block into cache fio --filename=/dev/mapper/cache --name=populate --rw=write --bs=4k \ --direct=1 --size=64k 3. Reload the cache into passthrough mode dmsetup suspend cache dmsetup reload cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 passthrough smq 0" dmsetup resume cache 4. Write to the first cached block concurrently fio --filename=/dev/mapper/cache --name test --rw=randwrite --bs=4k \ --randrepeat=0 --direct=1 --numjobs=2 --size 64k Fix by checking if mg->cell is valid before attempting to unlock it. Fixes: b29d4986d0da ("dm cache: significant rework to leverage dm-bio-prison-v2") Signed-off-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka Signed-off-by: Sasha Levin --- drivers/md/dm-cache-target.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 0d002d50329da..9c4aa5180a70e 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -1458,8 +1458,10 @@ static void invalidate_complete(struct dm_cache_migration *mg, bool success) struct cache *cache = mg->cache; bio_list_init(&bios); - if (dm_cell_unlock_v2(cache->prison, mg->cell, &bios)) - free_prison_cell(cache, mg->cell); + if (mg->cell) { + if (dm_cell_unlock_v2(cache->prison, mg->cell, &bios)) + free_prison_cell(cache, mg->cell); + } if (!success && mg->overwrite_bio) bio_io_error(mg->overwrite_bio); -- 2.53.0