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autofs: use path_has_submounts() to fix unreliable have_submount() checks 

If an automount mount is clone(2)ed into a file system that is propagation
private, when it later expires in the originating namespace, subsequent
calls to autofs ->d_automount() for that dentry in the original namespace
will return ELOOP until the mount is umounted in the cloned namespace.

Now that a struct path is available where needed use path_has_submounts()
instead of have_submounts() so we don't get false positives when checking
if a dentry is a mount point or contains mounts in the current namespace.

Link: http://lkml.kernel.org/r/20161011053423.27645.91233.stgit@pluto.themaw.net
Signed-off-by: Ian Kent <raven@themaw.net>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
zero-colors
Ian Kent 2016-11-24 08:03:42 +11:00 committed by Al Viro
parent cfaf86ab6c
commit 6035974147
3 changed files with 15 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/autofs4/dev-ioctl.c
View File

@ -575,7 +575,7 @@ static int autofs_dev_ioctl_ismountpoint(struct file *fp,
devid = new_encode_dev(dev);
err = have_submounts(path.dentry);
err = path_has_submounts(&path);
if (follow_down_one(&path))
magic = path.dentry->d_sb->s_magic;

14
fs/autofs4/root.c
View File

@ -384,16 +384,16 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
/*
* It's possible that user space hasn't removed directories
* after umounting a rootless multi-mount, although it
* should. For v5 have_submounts() is sufficient to handle
* this because the leaves of the directory tree under the
* mount never trigger mounts themselves (they have an autofs
* trigger mount mounted on them). But v4 pseudo direct mounts
* do need the leaves to trigger mounts. In this case we
* have no choice but to use the list_empty() check and
* should. For v5 path_has_submounts() is sufficient to
* handle this because the leaves of the directory tree under
* the mount never trigger mounts themselves (they have an
* autofs trigger mount mounted on them). But v4 pseudo direct
* mounts do need the leaves to trigger mounts. In this case
* we have no choice but to use the list_empty() check and
* require user space behave.
*/
if (sbi->version > 4) {
if (have_submounts(dentry)) {
if (path_has_submounts(path)) {
spin_unlock(&sbi->fs_lock);
goto done;
}

10
fs/autofs4/waitq.c
View File

@ -250,8 +250,9 @@ autofs4_find_wait(struct autofs_sb_info *sbi, const struct qstr *qstr)
static int validate_request(struct autofs_wait_queue **wait,
struct autofs_sb_info *sbi,
const struct qstr *qstr,
struct dentry *dentry, enum autofs_notify notify)
const struct path *path, enum autofs_notify notify)
{
struct dentry *dentry = path->dentry;
struct autofs_wait_queue *wq;
struct autofs_info *ino;
@ -314,6 +315,7 @@ static int validate_request(struct autofs_wait_queue **wait,
*/
if (notify == NFY_MOUNT) {
struct dentry *new = NULL;
struct path this;
int valid = 1;
/*
@ -333,7 +335,9 @@ static int validate_request(struct autofs_wait_queue **wait,
dentry = new;
}
}
if (have_submounts(dentry))
this.mnt = path->mnt;
this.dentry = dentry;
if (path_has_submounts(&this))
valid = 0;
if (new)
@ -406,7 +410,7 @@ int autofs4_wait(struct autofs_sb_info *sbi,
return -EINTR;
}
ret = validate_request(&wq, sbi, &qstr, dentry, notify);
ret = validate_request(&wq, sbi, &qstr, path, notify);
if (ret <= 0) {
if (ret != -EINTR)
mutex_unlock(&sbi->wq_mutex);