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 0E8913E0C70; Wed, 20 May 2026 17:24:38 +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=1779297879; cv=none; b=ToiwFvtDPEj5s6TIvmrvSMjvR9PXsMq7VCNRd9xAaMw3A/dlOc72AodcGvNAr6ruXjf26CNf8Mx16f/2MK3T+K4KZe4nYAS6iIe9eHk2u4lpsU2E4CeIoraIbXjaraedK0to5FMhQiVba0daoezvDNwTqqJ8fZnVzCBgQ8ieJKo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779297879; c=relaxed/simple; bh=JqNeRcebTJI6jn/gM8E/wsqSsmjWWiBHUYkv7JUbALc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dLBI7KWllfoB+PWWKk9rPUdFOFftMjJ5DbmM9ULeqAxf3wGJGnjpwg1gc7lm0u2k3gsTmQwzktR5y8FOXqGrTsyYvI6SgPBnJblnXUssj7v5D8mu4V4qVPzRqCuHG8BdBpGQav/YKCdt9PgYcBEG/pDCk5u7HKFKwgtds475jZI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=BIsnOnhZ; 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="BIsnOnhZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 712391F00893; Wed, 20 May 2026 17:24:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779297877; bh=6n5frZ+Dlz0UweCan3U7iXiyIwLEFabNg5qpe4M4jcs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=BIsnOnhZj0nItTWK1JALXpyzI6Z0KD7Hq0NgUIN95fPgLUZvei2fZrZrFbPtX4+p/ gFU7UGv6Su8ArPRD1TtmnoB1CLfUlMfizHKwwODVkhvGR2WHDO83tuiQmLVPWbln3b oGtuWVIrNmNbkkpeAaMlgCTk5YNrUgoyRi+D0Q4w= 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 6.18 198/957] dm cache: fix null-deref with concurrent writes in passthrough mode Date: Wed, 20 May 2026 18:11:21 +0200 Message-ID: <20260520162138.842971805@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260520162134.554764788@linuxfoundation.org> References: <20260520162134.554764788@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org 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: 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 7bad7cc87d370..1296965cf94cf 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -1462,8 +1462,10 @@ 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