From patchwork Wed Mar 29 20:24:06 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Disseldorp X-Patchwork-Id: 13193193 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D1C64C74A5B for ; Wed, 29 Mar 2023 20:23:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229650AbjC2UXT (ORCPT ); Wed, 29 Mar 2023 16:23:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39686 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229610AbjC2UXS (ORCPT ); Wed, 29 Mar 2023 16:23:18 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6EE340F4; Wed, 29 Mar 2023 13:23:16 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (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-out1.suse.de (Postfix) with ESMTPS id 79CB421A84; Wed, 29 Mar 2023 20:23:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1680121395; 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=BTYMUFJkxD7ap26/zj0eBSKlKQMHZZxSnbtlAEkWe1Q=; b=qnygApINZMMV+QaKx4jjtc/4/WD/rqNZUV5fXch+DLYG22AW2UF9yvk/vCM03LTRHPG3Lc rH+Ulcr14qu45mVsx4SiXKQGofcyS6q2p3/ewL1Rg/3jG0bVY1U3ennx+7GjXEhdOLUWYB 06we1NwV455a0aFQuJuZACZ1IyfGOuY= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1680121395; 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=BTYMUFJkxD7ap26/zj0eBSKlKQMHZZxSnbtlAEkWe1Q=; b=QLOwJlPk+Hl8LjyMo4vC90GgFbBVzpfGsrmP9ZhWeUqldBuRpcHcMudlWp0Fa5ZDthaV29 whD1lJ5dqGxyccBA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (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 imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 4F404138FF; Wed, 29 Mar 2023 20:23:15 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id HofTETOeJGSVZAAAMHmgww (envelope-from ); Wed, 29 Mar 2023 20:23:15 +0000 From: David Disseldorp To: linux-cifs@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, smfrench@gmail.com, David Disseldorp Subject: [PATCH] cifs: fix DFS traversal oops without CONFIG_CIFS_DFS_UPCALL Date: Wed, 29 Mar 2023 22:24:06 +0200 Message-Id: <20230329202406.15762-1-ddiss@suse.de> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org When compiled with CONFIG_CIFS_DFS_UPCALL disabled, cifs_dfs_d_automount NULL. cifs.ko logic for mapping CIFS_FATTR_DFS_REFERRAL attributes to S_AUTOMOUNT and corresponding dentry flags is retained regardless of CONFIG_CIFS_DFS_UPCALL, leading to a NULL pointer dereference in VFS follow_automount() when traversing a DFS referral link: BUG: kernel NULL pointer dereference, address: 0000000000000000 ... Call Trace: __traverse_mounts+0xb5/0x220 ? cifs_revalidate_mapping+0x65/0xc0 [cifs] step_into+0x195/0x610 ? lookup_fast+0xe2/0xf0 path_lookupat+0x64/0x140 filename_lookup+0xc2/0x140 ? __create_object+0x299/0x380 ? kmem_cache_alloc+0x119/0x220 ? user_path_at_empty+0x31/0x50 user_path_at_empty+0x31/0x50 __x64_sys_chdir+0x2a/0xd0 ? exit_to_user_mode_prepare+0xca/0x100 do_syscall_64+0x42/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc This fix adds an inline cifs_dfs_d_automount() {return -EREMOTE} handler when CONFIG_CIFS_DFS_UPCALL is disabled. An alternative would be to avoid flagging S_AUTOMOUNT, etc. without CONFIG_CIFS_DFS_UPCALL. This approach was chosen as it provides more control over the error path. Signed-off-by: David Disseldorp --- fs/cifs/cifsfs.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h index 71fe0a0a7992..415176b2cf32 100644 --- a/fs/cifs/cifsfs.h +++ b/fs/cifs/cifsfs.h @@ -124,7 +124,10 @@ extern const struct dentry_operations cifs_ci_dentry_ops; #ifdef CONFIG_CIFS_DFS_UPCALL extern struct vfsmount *cifs_dfs_d_automount(struct path *path); #else -#define cifs_dfs_d_automount NULL +static inline struct vfsmount *cifs_dfs_d_automount(struct path *path) +{ + return ERR_PTR(-EREMOTE); +} #endif /* Functions related to symlinks */