On Mon, 09 Sep 2013 15:18:00 +0800 Ian Kent <[email protected]> wrote:
> On Sun, 2013-09-08 at 07:33 -0400, Jeff Layton wrote: > > On Sun, 08 Sep 2013 16:47:23 +0800 > > Ian Kent <[email protected]> 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 <[email protected]> > > > Cc: Jeff Layton <[email protected]> > > > Cc: Al Viro <[email protected]> > > > --- > > > 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. > > In both cases the path comes from a structure passed from user space. > So I started thinking it wasn't correct previously. > AFAICT, this is a kernel string by the time it gets here. _autofs_dev_ioctl calls copy_dev_ioctl, which copies that struct from userland to a kernel buffer. > > > > > 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 <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
