On Sun, 08 Sep 2013 16:47:23 +0800
Ian Kent <raven@xxxxxxxxxx> wrote:
> When reconnecting to automounts at startup an autofs ioctl is used
> to find the device and inode of existing mounts so they can be used
> to open a file descriptor of possibly covered mounts.
>
> At this time the the caller might not yet "own" the mount so it can
> trigger calling ->d_automount(). This causes automount to hang when
> trying to reconnect to direct or offset mount types.
>
> Consequently kern_path() can't be used but path_mntpointat() can be.
>
> Signed-off-by: Ian Kent <raven@xxxxxxxxxx>
> Cc: Jeff Layton <jlayton@xxxxxxxxxx>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---
> fs/autofs4/dev-ioctl.c | 23 ++++++++++++-----------
> 1 file changed, 12 insertions(+), 11 deletions(-)
>
> diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
> index 9183821..228866f 100644
> --- a/fs/autofs4/dev-ioctl.c
> +++ b/fs/autofs4/dev-ioctl.c
> @@ -183,13 +183,14 @@ static int autofs_dev_ioctl_protosubver(struct file *fp,
> return 0;
> }
>
> +/* Find the topmost mount satisfying test() */
> static int find_autofs_mount(const char *pathname,
> struct path *res,
> int test(struct path *path, void *data),
> void *data)
> {
> struct path path;
> - int err = kern_path(pathname, 0, &path);
> + int err = user_path_mntpointat(AT_FDCWD, pathname, 0, &path);
This looks wrong. "pathname" is a kernel string, not a __user one. I
think what you need to do here is to turn user_path_mntpointat into a
wrapper around a kern_path_mntpointat equivalent and then call that
here.
> if (err)
> return err;
> err = -ENOENT;
> @@ -197,10 +198,9 @@ static int find_autofs_mount(const char *pathname,
> if (path.dentry->d_sb->s_magic == AUTOFS_SUPER_MAGIC) {
> if (test(&path, data)) {
> path_get(&path);
> - if (!err) /* already found some */
> - path_put(res);
> *res = path;
> err = 0;
> + break;
> }
> }
> if (!follow_up(&path))
> @@ -498,12 +498,11 @@ static int autofs_dev_ioctl_askumount(struct file *fp,
> * mount if there is one or 0 if it isn't a mountpoint.
> *
> * If we aren't supplied with a file descriptor then we
> - * lookup the nameidata of the path and check if it is the
> - * root of a mount. If a type is given we are looking for
> - * a particular autofs mount and if we don't find a match
> - * we return fail. If the located nameidata path is the
> - * root of a mount we return 1 along with the super magic
> - * of the mount or 0 otherwise.
> + * lookup the path and check if it is the root of a mount.
> + * If a type is given we are looking for a particular autofs
> + * mount and if we don't find a match we return fail. If the
> + * located path is the root of a mount we return 1 along with
> + * the super magic of the mount or 0 otherwise.
> *
> * In both cases the the device number (as returned by
> * new_encode_dev()) is also returned.
> @@ -531,9 +530,11 @@ static int autofs_dev_ioctl_ismountpoint(struct file *fp,
>
> if (!fp || param->ioctlfd == -1) {
> if (autofs_type_any(type))
> - err = kern_path(name, LOOKUP_FOLLOW, &path);
> + err = user_path_mntpointat(AT_FDCWD,
> + name, LOOKUP_FOLLOW, &path);
> else
> - err = find_autofs_mount(name, &path, test_by_type, &type);
> + err = find_autofs_mount(name, &path,
> + test_by_type, &type);
...ditto in these spots of course...
> if (err)
> goto out;
> devid = new_encode_dev(path.dentry->d_sb->s_dev);
>
--
Jeff Layton <jlayton@xxxxxxxxxx>
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