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autofs4 - fix device ioctl mount lookup

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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 kern_path_mountpoint() can be.

Signed-off-by: Ian Kent <raven@themaw.net>
Cc: Jeff Layton <jlayton@redhat.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Ian Kent 2013-09-08 16:47:23 +08:00 committed by Al Viro
parent 2d86465101
commit ac83871996
1 changed files with 12 additions and 11 deletions
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23
fs/autofs4/dev-ioctl.c
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@ -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 = kern_path_mountpoint(AT_FDCWD, pathname, &path, 0);
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))
@ -486,12 +486,11 @@ 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.
@ -519,9 +518,11 @@ 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 = kern_path_mountpoint(AT_FDCWD,
name, &path, LOOKUP_FOLLOW);
else
err = find_autofs_mount(name, &path, test_by_type, &type);
err = find_autofs_mount(name, &path,
test_by_type, &type);
if (err)
goto out;
devid = new_encode_dev(path.dentry->d_sb->s_dev);