This fix looks correct and urgent, although if we have time I would
like to try it for another day before requesting merge to linux-2.6
The dfs documentation does state that we should be sending \ rather
than \\ (although earlier places in the document stated the reverse,
it is more clear later in the network documentation).
On Mon, Dec 15, 2008 at 7:02 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> The paths in a DFS request are supposed to only have a single preceding
> backslash, but we are sending them with a double backslash. This is
> exposing a bug in Windows where it also sends a path in the response
> that has a double backslash.
>
> The existing code that builds the mount option string however expects a
> double backslash prefix in a couple of places when it tries to use the
> path returned by build_path_from_dentry. Fix compose_mount_options to
> expect properly formed DFS paths (single backslash at front).
>
> Also clean up error handling in that function. There was a possible
> NULL pointer dereference and situations where a partially built option
> string would be returned.
>
> Tested against Samba 3.0.28-ish server and Win2k8.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> fs/cifs/cifs_dfs_ref.c | 48 ++++++++++++++++++++++++++++++++++++------------
> 1 files changed, 36 insertions(+), 12 deletions(-)
>
> diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
> index e1c1836..85c0a74 100644
> --- a/fs/cifs/cifs_dfs_ref.c
> +++ b/fs/cifs/cifs_dfs_ref.c
> @@ -122,7 +122,7 @@ static char *compose_mount_options(const char *sb_mountdata,
> char **devname)
> {
> int rc;
> - char *mountdata;
> + char *mountdata = NULL;
> int md_len;
> char *tkn_e;
> char *srvIP = NULL;
> @@ -136,10 +136,9 @@ static char *compose_mount_options(const char *sb_mountdata,
> *devname = cifs_get_share_name(ref->node_name);
> rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
> if (rc != 0) {
> - cERROR(1, ("%s: Failed to resolve server part of %s to IP",
> - __func__, *devname));
> - mountdata = ERR_PTR(rc);
> - goto compose_mount_options_out;
> + cERROR(1, ("%s: Failed to resolve server part of %s to IP: %d",
> + __func__, *devname, rc));;
> + goto compose_mount_options_err;
> }
> /* md_len = strlen(...) + 12 for 'sep+prefixpath='
> * assuming that we have 'unc=' and 'ip=' in
> @@ -149,8 +148,8 @@ static char *compose_mount_options(const char *sb_mountdata,
> strlen(ref->node_name) + 12;
> mountdata = kzalloc(md_len+1, GFP_KERNEL);
> if (mountdata == NULL) {
> - mountdata = ERR_PTR(-ENOMEM);
> - goto compose_mount_options_out;
> + rc = -ENOMEM;
> + goto compose_mount_options_err;
> }
>
> /* copy all options except of unc,ip,prefixpath */
> @@ -197,18 +196,32 @@ static char *compose_mount_options(const char *sb_mountdata,
>
> /* find & copy prefixpath */
> tkn_e = strchr(ref->node_name + 2, '\\');
> - if (tkn_e == NULL) /* invalid unc, missing share name*/
> - goto compose_mount_options_out;
> + if (tkn_e == NULL) {
> + /* invalid unc, missing share name*/
> + rc = -EINVAL;
> + goto compose_mount_options_err;
> + }
>
> + /*
> + * this function gives us a path with a double backslash prefix. We
> + * require a single backslash for DFS. Temporarily increment fullpath
> + * to put it in the proper form and decrement before freeing it.
> + */
> fullpath = build_path_from_dentry(dentry);
> + if (!fullpath) {
> + rc = -ENOMEM;
> + goto compose_mount_options_err;
> + }
> + ++fullpath;
> tkn_e = strchr(tkn_e + 1, '\\');
> - if (tkn_e || strlen(fullpath) - (ref->path_consumed)) {
> + if (tkn_e || (strlen(fullpath) - ref->path_consumed)) {
> strncat(mountdata, &sep, 1);
> strcat(mountdata, "prefixpath=");
> if (tkn_e)
> strcat(mountdata, tkn_e + 1);
> - strcat(mountdata, fullpath + (ref->path_consumed));
> + strcat(mountdata, fullpath + ref->path_consumed);
> }
> + --fullpath;
> kfree(fullpath);
>
> /*cFYI(1,("%s: parent mountdata: %s", __func__,sb_mountdata));*/
> @@ -217,6 +230,11 @@ static char *compose_mount_options(const char *sb_mountdata,
> compose_mount_options_out:
> kfree(srvIP);
> return mountdata;
> +
> +compose_mount_options_err:
> + kfree(mountdata);
> + mountdata = ERR_PTR(rc);
> + goto compose_mount_options_out;
> }
>
>
> @@ -309,13 +327,19 @@ cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
> goto out_err;
> }
>
> + /*
> + * The MSDFS spec states that paths in DFS referral requests and
> + * responses must be prefixed by a single '\' character instead of
> + * the double backslashes usually used in the UNC. This function
> + * gives us the latter, so we must adjust the result.
> + */
> full_path = build_path_from_dentry(dentry);
> if (full_path == NULL) {
> rc = -ENOMEM;
> goto out_err;
> }
>
> - rc = get_dfs_path(xid, ses , full_path, cifs_sb->local_nls,
> + rc = get_dfs_path(xid, ses , full_path + 1, cifs_sb->local_nls,
> &num_referrals, &referrals,
> cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
>
> --
> 1.5.5.1
>
>
--
Thanks,
Steve
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