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 AC9235683 for ; Mon, 3 Apr 2023 14:18:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1259EC433D2; Mon, 3 Apr 2023 14:18:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1680531507; bh=8Pwj6AeMV46wNGCGpoLrwR2GMOr61qL/EjWdxw7+qj8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PNBhHjlQLshDViqbTc1kMbnlkEteFNKjPvOe5ab9RFvZhfEAs8SZOZDbCwnBxFHGw owgKNlZ8Pn2XGCva8F5cdFBDsJc2Mi0ugt+1CUUIeiPeoGrTwpZ6m/T3CnHUsymDPI Jvl2SCuvH9tnqybLzedKtSRTV9rfHHF+4cSfiZ6c= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, David Disseldorp , "Paulo Alcantara (SUSE)" , Ronnie Sahlberg , Steve French Subject: [PATCH 4.19 70/84] cifs: fix DFS traversal oops without CONFIG_CIFS_DFS_UPCALL Date: Mon, 3 Apr 2023 16:09:11 +0200 Message-Id: <20230403140355.850086402@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230403140353.406927418@linuxfoundation.org> References: <20230403140353.406927418@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: David Disseldorp commit 179a88a8558bbf42991d361595281f3e45d7edfc upstream. When compiled with CONFIG_CIFS_DFS_UPCALL disabled, cifs_dfs_d_automount is 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 Cc: stable@vger.kernel.org Reviewed-by: Paulo Alcantara (SUSE) Reviewed-by: Ronnie Sahlberg Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- fs/cifs/cifsfs.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/fs/cifs/cifsfs.h +++ b/fs/cifs/cifsfs.h @@ -121,7 +121,10 @@ extern const struct dentry_operations ci #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 */