Commit 5e2fd17f authored by Paulo Alcantara's avatar Paulo Alcantara Committed by Steve French
Browse files

smb: client: fix mount when dns_resolver key is not available 



There was a wrong assumption that with CONFIG_CIFS_DFS_UPCALL=y there
would always be a dns_resolver key set up so we could unconditionally
upcall to resolve UNC hostname rather than using the value provided by
mount(2).

Only require it when performing automount of junctions within a DFS
share so users that don't have dns_resolver key still can mount their
regular shares with server hostname resolved by mount.cifs(8).

Fixes: 348a04a8 ("smb: client: get rid of dfs code dep in namespace.c")
Cc: stable@vger.kernel.org
Tested-by: default avatarEduard Bachmakov <e.bachmakov@gmail.com>
Reported-by: default avatarEduard Bachmakov <e.bachmakov@gmail.com>
Closes: https://lore.kernel.org/all/CADCRUiNvZuiUZ0VGZZO9HRyPyw6x92kiA7o7Q4tsX5FkZqUkKg@mail.gmail.com/


Signed-off-by: default avatarPaulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 5923d668

fs/smb/client/dfs.c

+13 −5
Original line number Diff line number Diff line
@@ -263,15 +263,23 @@ static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx) 
	return rc;

}



/* Resolve UNC hostname in @ctx->source and set ip addr in @ctx->dstaddr */

/*

 * If @ctx->dfs_automount, then update @ctx->dstaddr earlier with the DFS root

 * server from where we'll start following any referrals.  Otherwise rely on the

 * value provided by mount(2) as the user might not have dns_resolver key set up

 * and therefore failing to upcall to resolve UNC hostname under @ctx->source.

 */

static int update_fs_context_dstaddr(struct smb3_fs_context *ctx)

{

	struct sockaddr *addr = (struct sockaddr *)&ctx->dstaddr;

	int rc;

	int rc = 0;



	if (!ctx->nodfs && ctx->dfs_automount) {

		rc = dns_resolve_server_name_to_ip(ctx->source, addr, NULL);

		if (!rc)

			cifs_set_port(addr, ctx->port);

		ctx->dfs_automount = false;

	}

	return rc;

}

fs/smb/client/fs_context.h

+1 −0
Original line number Diff line number Diff line
@@ -268,6 +268,7 @@ struct smb3_fs_context { 
	bool witness:1; /* use witness protocol */

	char *leaf_fullpath;

	struct cifs_ses *dfs_root_ses;

	bool dfs_automount:1; /* set for dfs automount only */

};



extern const struct fs_parameter_spec smb3_fs_parameters[];

fs/smb/client/namespace.c

+15 −2
Original line number Diff line number Diff line
@@ -117,6 +117,18 @@ cifs_build_devname(char *nodename, const char *prepath) 
	return dev;

}



static bool is_dfs_mount(struct dentry *dentry)

{

	struct cifs_sb_info *cifs_sb = CIFS_SB(dentry->d_sb);

	struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);

	bool ret;



	spin_lock(&tcon->tc_lock);

	ret = !!tcon->origin_fullpath;

	spin_unlock(&tcon->tc_lock);

	return ret;

}



/* Return full path out of a dentry set for automount */

static char *automount_fullpath(struct dentry *dentry, void *page)

{
@@ -212,8 +224,9 @@ static struct vfsmount *cifs_do_automount(struct path *path) 
		ctx->source = NULL;

		goto out;

	}

	cifs_dbg(FYI, "%s: ctx: source=%s UNC=%s prepath=%s\n",

		 __func__, ctx->source, ctx->UNC, ctx->prepath);

	ctx->dfs_automount = is_dfs_mount(mntpt);

	cifs_dbg(FYI, "%s: ctx: source=%s UNC=%s prepath=%s dfs_automount=%d\n",

		 __func__, ctx->source, ctx->UNC, ctx->prepath, ctx->dfs_automount);



	mnt = fc_mount(fc);

out: