Commit dad80c6b authored by David Howells's avatar David Howells Committed by Steve French
Browse files

cifs: Fix reacquisition of volume cookie on still-live connection 



During mount, cifs_mount_get_tcon() gets a tcon resource connection record
and then attaches an fscache volume cookie to it.  However, it does this
irrespective of whether or not the tcon returned from cifs_get_tcon() is a
new record or one that's already in use.  This leads to a warning about a
volume cookie collision and a leaked volume cookie because tcon->fscache
gets reset.

Fix this be adding a mutex and a "we've already tried this" flag and only
doing it once for the lifetime of the tcon.

[!] Note: Looking at cifs_mount_get_tcon(), a more general solution may
actually be required.  Reacquiring the volume cookie isn't the only thing
that function does: it also partially reinitialises the tcon record without
any locking - which may cause live filesystem ops already using the tcon
through a previous mount to malfunction.

This can be reproduced simply by something like:

    mount //example.com/test /xfstest.test -o user=shares,pass=xxx,fsc
    mount //example.com/test /mnt -o user=shares,pass=xxx,fsc

Fixes: 70431bfd ("cifs: Support fscache indexing rewrite")
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Acked-by: default avatarPaulo Alcantara (Red Hat) <pc@manguebit.com>
cc: Shyam Prasad N <sprasad@microsoft.com>
cc: linux-cifs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 0bbac3fa

fs/smb/client/cifsglob.h

+2 −0
Original line number Diff line number Diff line
@@ -1276,7 +1276,9 @@ struct cifs_tcon { 
	__u32 max_cached_dirs;

#ifdef CONFIG_CIFS_FSCACHE

	u64 resource_id;		/* server resource id */

	bool fscache_acquired;		/* T if we've tried acquiring a cookie */

	struct fscache_volume *fscache;	/* cookie for share */

	struct mutex fscache_lock;	/* Prevent regetting a cookie */

#endif

	struct list_head pending_opens;	/* list of incomplete opens */

	struct cached_fids *cfids;

fs/smb/client/fscache.c

+13 −0
Original line number Diff line number Diff line
@@ -43,12 +43,23 @@ int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon) 
	char *key;

	int ret = -ENOMEM;



	if (tcon->fscache_acquired)

		return 0;



	mutex_lock(&tcon->fscache_lock);

	if (tcon->fscache_acquired) {

		mutex_unlock(&tcon->fscache_lock);

		return 0;

	}

	tcon->fscache_acquired = true;



	tcon->fscache = NULL;

	switch (sa->sa_family) {

	case AF_INET:

	case AF_INET6:

		break;

	default:

		mutex_unlock(&tcon->fscache_lock);

		cifs_dbg(VFS, "Unknown network family '%d'\n", sa->sa_family);

		return -EINVAL;

	}
@@ -57,6 +68,7 @@ int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon) 


	sharename = extract_sharename(tcon->tree_name);

	if (IS_ERR(sharename)) {

		mutex_unlock(&tcon->fscache_lock);

		cifs_dbg(FYI, "%s: couldn't extract sharename\n", __func__);

		return PTR_ERR(sharename);

	}
@@ -90,6 +102,7 @@ int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon) 
	kfree(key);

out:

	kfree(sharename);

	mutex_unlock(&tcon->fscache_lock);

	return ret;

}

fs/smb/client/misc.c

+3 −0
Original line number Diff line number Diff line
@@ -139,6 +139,9 @@ tcon_info_alloc(bool dir_leases_enabled) 
	atomic_set(&ret_buf->num_local_opens, 0);

	atomic_set(&ret_buf->num_remote_opens, 0);

	ret_buf->stats_from_time = ktime_get_real_seconds();

#ifdef CONFIG_CIFS_FSCACHE

	mutex_init(&ret_buf->fscache_lock);

#endif



	return ret_buf;

}