On Mon, 19 Mar 2012 18:21:28 -0400
Thomas Hadig <thomas.hadig@xxxxxxxxxx> wrote:
> Hi,
>
> I am using the CIFS module from Linux kernel 3.2.9.
>
> We have the following setup:
>
> In DNS, domain.net resolves to our secondary AD server ad2.domain.net
> Our primary domain controller is ad1.domain.net and has a DFS redirection set up from \\ad1\share\Users to \\files\share\Users.
>
> When mounting \\domain.net\share\Users I get an error.
>
> I traced this down to the cifs_mount function in fs/cifs/connect.c. In there, rc is set to 0 at the beginning but never reset.
> In short, adding an rc=0; line after the label try_mount_again: fixes the issue.
>
> Detailed information:
> - Connecting to \\domain.net\share\Users connects to ad2 with a SMB_COM_NEGOTIATE, SMB_COM_SESSION_SETUP_ANDX, and SMB_COM_TREE_CONNECT_ANDX.
> - SMB_COM_TREE_CONNECT_ANDX fails with STATUS_BAD_NETWORK_NAME causing rc to be non-zero and jumping to remote_path_check:
> - It connects to ad2's IPC$ share and retrieves the DFS_REFERRAL which leads to \\ad1\share and jumps to try_mount_again:
> - It closes the samba session to ad2.
> - Now, it connects to ad1 with SMB_COM_NEGOTIATE, SMB_COM_SESSION_SETUP_ANDX, and SMB_COM_TREE_CONNECT_ANDX.
> - This time, it succeeds and continues with SMB_COM_TRANSACTION2/ TRANS2_QUERY_FS_INFORMATION/SMB_QUERY_FS_DEVICE_INFO and SMB_QUERY_FS_ATTRIBUTE_INFO.
> - It comes to:
> /* check if a whole path is not remote */
> if (!rc && tcon) {
> /* build_path_to_root works only when we have a valid tcon */
> where rc is still non-zero and, thus, does NOT check again for a DFS_REFERRAL.
> - I closes the samba session to ad1 and exists with the -6 mount error from the initial tree connect.
>
> The correct behavior would be to reset rc to 0 when connecting to a different samba session.
>
>
> Patch info:
>
> rc = bdi_setup_and_register(&cifs_sb->bdi, "cifs", BDI_CAP_MAP_COPY);
> if (rc)
> return rc;
>
> #ifdef CONFIG_CIFS_DFS_UPCALL
> try_mount_again:
> /* cleanup activities if we're chasing a referral */
> if (referral_walks_count) {
> if (tcon)
> cifs_put_tcon(tcon);
> else if (pSesInfo)
> cifs_put_smb_ses(pSesInfo);
>
> FreeXid(xid);
> }
> #endif
> tcon = NULL;
> pSesInfo = NULL;
> srvTcp = NULL;
> full_path = NULL;
> tlink = NULL;
> + rc=0;
>
> xid = GetXid();
>
> /* get a reference to a tcp session */
> srvTcp = cifs_get_tcp_session(volume_info);
> if (IS_ERR(srvTcp)) {
> rc = PTR_ERR(srvTcp);
> bdi_destroy(&cifs_sb->bdi);
> goto out;
> }
>
>
>
> Thanks
> Thomas
>
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Nice analysis. That looks correct to me too...
Care to spin up a patch with a description and signed-off-by line? You
can add my Reviewed-by if so...
--
Jeff Layton <jlayton@xxxxxxxxxx>
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