From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 7B47E8F57 for ; Sun, 16 Jul 2023 20:49:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F1C1EC433C7; Sun, 16 Jul 2023 20:49:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1689540560; bh=TXdBClRXVvi48yJrwfyN5ghEtX7rxVGUBD6tVegiZis=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=r1vbL5xDa2/bGP7tHBQpN8jW8drxQgll7f/fnLQs6t6QkOYqhSA5KMX2IE1qXoDSk JHuuPfZFIc2dyTTCummSMwF2lxLoyDgTinuYkgzXEYetCbPatuOIDibt/8YyrExQ4t Cn+UJJJpvmWrpvtAUrbk8E0EMiHKph78lGE6fz5o= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Christoph Hellwig , Demi Marie Obenour , Christoph Hellwig , Jens Axboe Subject: [PATCH 6.1 379/591] block: increment diskseq on all media change events Date: Sun, 16 Jul 2023 21:48:38 +0200 Message-ID: <20230716194933.726121320@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230716194923.861634455@linuxfoundation.org> References: <20230716194923.861634455@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Demi Marie Obenour commit b90ecc0379eb7bbe79337b0c7289390a98752646 upstream. Currently, associating a loop device with a different file descriptor does not increment its diskseq. This allows the following race condition: 1. Program X opens a loop device 2. Program X gets the diskseq of the loop device. 3. Program X associates a file with the loop device. 4. Program X passes the loop device major, minor, and diskseq to something. 5. Program X exits. 6. Program Y detaches the file from the loop device. 7. Program Y attaches a different file to the loop device. 8. The opener finally gets around to opening the loop device and checks that the diskseq is what it expects it to be. Even though the diskseq is the expected value, the result is that the opener is accessing the wrong file. >>From discussions with Christoph Hellwig, it appears that disk_force_media_change() was supposed to call inc_diskseq(), but in fact it does not. Adding a Fixes: tag to indicate this. Christoph's Reported-by is because he stated that disk_force_media_change() calls inc_diskseq(), which is what led me to discover that it should but does not. Reported-by: Christoph Hellwig Signed-off-by: Demi Marie Obenour Fixes: e6138dc12de9 ("block: add a helper to raise a media changed event") Cc: stable@vger.kernel.org # 5.15+ Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/20230607170837.1559-1-demi@invisiblethingslab.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/disk-events.c | 1 + 1 file changed, 1 insertion(+) --- a/block/disk-events.c +++ b/block/disk-events.c @@ -307,6 +307,7 @@ bool disk_force_media_change(struct gend if (!(events & DISK_EVENT_MEDIA_CHANGE)) return false; + inc_diskseq(disk); if (__invalidate_device(disk->part0, true)) pr_warn("VFS: busy inodes on changed media %s\n", disk->disk_name);