From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84290C4338F for ; Fri, 6 Aug 2021 10:24:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5FD7D61163 for ; Fri, 6 Aug 2021 10:24:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245062AbhHFKYh (ORCPT ); Fri, 6 Aug 2021 06:24:37 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:39044 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245151AbhHFKYf (ORCPT ); Fri, 6 Aug 2021 06:24:35 -0400 Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 122F620280; Fri, 6 Aug 2021 10:24:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1628245459; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=nugh0SRsvW+C6UUVbvqWlc+sAgjtlJFQnDtQLIB1ZHc=; b=vI4Lqo6/jTHFtYlltkNYUXncytnykW6Xjk5OwOG+H5MbfN+nNV4x7jZNdLxJLHgpMMxCyh zGoArgvK6kfY8WjVOoVJcRlPZ93tWDFGrlRV2zEK/QmvhhMnpwQ3OTEK6HHyWQ77Et19LU JzyOc+ECZnLKjnIQlJjtAi74WYAOJwE= Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap1.suse-dmz.suse.de (Postfix) with ESMTPS id 0781113A79; Fri, 6 Aug 2021 10:24:17 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap1.suse-dmz.suse.de with ESMTPSA id 3WSSLdENDWGuTAAAGKfGzw (envelope-from ); Fri, 06 Aug 2021 10:24:17 +0000 From: Qu Wenruo To: linux-btrfs@vger.kernel.org Cc: butt3rflyh4ck Subject: [PATCH] btrfs: fix NULL pointer dereference when deleting device by invalid id Date: Fri, 6 Aug 2021 18:24:15 +0800 Message-Id: <20210806102415.304717-1-wqu@suse.com> X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org [BUG] It's super easy to trigger NULL pointer dereference, just by removing a non-exist device id: # mkfs.btrfs -f -m single -d single /dev/test/scratch1 \ /dev/test/scratch2 # mount /dev/test/scratch1 /mnt/btrfs # btrfs device remove 3 /mnt/btrfs Then we have the following kernel NULL pointer dereference: BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 9 PID: 649 Comm: btrfs Not tainted 5.14.0-rc3-custom+ #35 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:btrfs_rm_device+0x4de/0x6b0 [btrfs] btrfs_ioctl+0x18bb/0x3190 [btrfs] ? lock_is_held_type+0xa5/0x120 ? find_held_lock.constprop.0+0x2b/0x80 ? do_user_addr_fault+0x201/0x6a0 ? lock_release+0xd2/0x2d0 ? __x64_sys_ioctl+0x83/0xb0 __x64_sys_ioctl+0x83/0xb0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae [CAUSE] Commit a27a94c2b0c7 ("btrfs: Make btrfs_find_device_by_devspec return btrfs_device directly") moves the "missing" device path check into btrfs_rm_device(). But btrfs_rm_device() itself can have case where it only receives @devid, with NULL as @device_path. In that case, calling strcmp() on NULL will trigger the NULL pointer dereference. Before that commit, we handle the "missing" case inside btrfs_find_device_by_devspec(), which will not check @device_path at all if @devid is provided, thus no way to trigger the bug. [FIX] Before calling strcmp(), also make sure @device_path is not NULL. Fixes: a27a94c2b0c7 ("btrfs: Make btrfs_find_device_by_devspec return btrfs_device directly") Reported-by: butt3rflyh4ck Signed-off-by: Qu Wenruo --- fs/btrfs/volumes.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 230192d097c4..5156254a9655 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2079,7 +2079,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path, if (IS_ERR(device)) { if (PTR_ERR(device) == -ENOENT && - strcmp(device_path, "missing") == 0) + device_path && strcmp(device_path, "missing") == 0) ret = BTRFS_ERROR_DEV_MISSING_NOT_FOUND; else ret = PTR_ERR(device); -- 2.32.0