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 D88973F8EC0; Wed, 20 May 2026 18:06:54 +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=1779300416; cv=none; b=soNB49g3FkqOv+hfj8RY051sLkCoUgFiNVb3r96bb87e+e1Hv3q/Ie3nhtE5J7Zi0ah1NDVwBdzTwct27jlcMd/pOOFsXoYjSsealiXssoAflNZct1tDPt5mu+vo9hM0OV8toLYT4oQGkIZBrv8HEFRra1KkRc724hTRpN7IX5c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779300416; c=relaxed/simple; bh=5V7pSkC9Uamhic0P4AnIls4w9Zc4ie50/53KRvpkIjw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=k4dSGjU54WyKVB+I+MccnreIEiW3gzBADRgzKUZzyowYUaHp8XDiTbTi+IUPMkEP5UufoKUaC/5oqbxsyjhwlLdhme/P7YyhROHZQHkJtWuri9QNr3oVxepJ5njlc5CPHTV6StDLfU+96uG77VNQol68RWq/qM6FvVzoVGkFARY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=LefGUzn2; 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="LefGUzn2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3A511F000E9; Wed, 20 May 2026 18:06:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779300414; bh=zPh66RBQc91IsJkU7eSygsRySK8tlmdivruiLRA2Cm0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LefGUzn2ryjEwGIjW3GBsyUsq42O3N9IrUmqZ0Z+QYCJNUtvYBrIEZrCfpOMTCN1P AnazlUDtfs4E6IRy1L38GwYv2ZINIXPzWOR4a5sKAcGwBnfPLMDuzWOOB2c6T79Vup /ifP/f8Zf6Osd0o+K4fOeNo4LDDY8Ymg3XA6kgT0= 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 6.12 125/666] dm cache: fix null-deref with concurrent writes in passthrough mode Date: Wed, 20 May 2026 18:15:36 +0200 Message-ID: <20260520162113.925778665@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260520162111.222830634@linuxfoundation.org> References: <20260520162111.222830634@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 6.12-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 6aa4095dc5876..c1e94ffc9b3d6 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -1456,8 +1456,10 @@ 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