From patchwork Sun Jan 21 20:26:34 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Ehrhardt X-Patchwork-Id: 13524669 Received: from cae.in-ulm.de (cae.in-ulm.de [217.10.14.231]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 209C337713; Sun, 21 Jan 2024 20:27:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.10.14.231 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705868832; cv=none; b=aRwVA+srv5ScTzk0sug1oz6M77CKZ2dZOYXYOescMKaOXzOVkyYWJJfBrZV/Bqp/sfCt4lWW9A6NWqKoaZqa4rCwVl6VHAOoc8nULQYbrqbJYmCKE4Xbjq5BXj3aEjObP5r+8SWiJPsqZc4Xb4i5fVmOgz3Ol61RQnCIRWABUAI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705868832; c=relaxed/simple; bh=uZiztjpinSS7Xdrx+6z3yfBDTTHpVfueyyjwSZhYKaI=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=eopHBvg1iodqMpDfMtbmeSLfUv7CotjnhnT57vw//kzpiPqv8kBLMRCEtT0FfJJnUAGGwagWPz6KXcq8JcumDlEIFgtkAYGEqTfzXdMnmdKmnX6GfGVOL6dDfnyRCbijbv4WzPnmDL4Wp2ivl6Io4gpBQ0qkoj2ipPeASLFDd5U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=c--e.de; spf=pass smtp.mailfrom=c--e.de; arc=none smtp.client-ip=217.10.14.231 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=c--e.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=c--e.de Received: by cae.in-ulm.de (Postfix, from userid 1000) id DBDBE1401CF; Sun, 21 Jan 2024 21:27:00 +0100 (CET) From: "Christian A. Ehrhardt" To: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: "Christian A. Ehrhardt" , syzbot+a532b03fdfee2c137666@syzkaller.appspotmail.com, syzbot+63dec323ac56c28e644f@syzkaller.appspotmail.com, Jens Axboe , Andrew Morton , Alexander Viro Subject: [PATCH] block: Fix WARNING in _copy_from_iter Date: Sun, 21 Jan 2024 21:26:34 +0100 Message-Id: <20240121202634.275068-1-lk@c--e.de> X-Mailer: git-send-email 2.30.2 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Syzkaller reports a warning in _copy_from_iter because an iov_iter is supposedly used in the wrong direction. The reason is that syzcaller managed to generate a request with a transfer direction of SG_DXFER_TO_FROM_DEV. This instructs the kernel to copy user buffers into the kernel, read into the copied buffers and then copy the data back to user space. Thus the iovec is used in both directions. Detect this situation in the block layer and construct a new iterator with the correct direction for the copy-in. Reported-by: syzbot+a532b03fdfee2c137666@syzkaller.appspotmail.com Closes: https://lore.kernel.org/lkml/0000000000009b92c10604d7a5e9@google.com/t/ Reported-by: syzbot+63dec323ac56c28e644f@syzkaller.appspotmail.com Closes: https://lore.kernel.org/lkml/0000000000003faaa105f6e7c658@google.com/T/ Signed-off-by: Christian A. Ehrhardt Reviewed-by: Christoph Hellwig --- block/blk-map.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/block/blk-map.c b/block/blk-map.c index 8584babf3ea0..71210cdb3442 100644 --- a/block/blk-map.c +++ b/block/blk-map.c @@ -205,12 +205,19 @@ static int bio_copy_user_iov(struct request *rq, struct rq_map_data *map_data, /* * success */ - if ((iov_iter_rw(iter) == WRITE && - (!map_data || !map_data->null_mapped)) || - (map_data && map_data->from_user)) { + if (iov_iter_rw(iter) == WRITE && + (!map_data || !map_data->null_mapped)) { ret = bio_copy_from_iter(bio, iter); if (ret) goto cleanup; + } else if (map_data && map_data->from_user) { + struct iov_iter iter2 = *iter; + + /* This is the copy-in part of SG_DXFER_TO_FROM_DEV. */ + iter2.data_source = ITER_SOURCE; + ret = bio_copy_from_iter(bio, &iter2); + if (ret) + goto cleanup; } else { if (bmd->is_our_pages) zero_fill_bio(bio);