[PATCH 7/8] autofs - use path_has_submounts() to fix unreliable have_submount() checks

Ian Kent
2016-10-11T05:34:30Z

From: Ian Kent <ikent@redhat.com>

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.

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>
---
fs/autofs4/dev-ioctl.c | 2 +-
fs/autofs4/root.c | 14 +++++++-------
fs/autofs4/waitq.c | 10 +++++++---
3 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index 40c69f9..afacdaa 100644
--- a/fs/autofs4/dev-ioctl.c
+++ b/fs/autofs4/dev-ioctl.c
@@ -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;
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index d7e48fe..c4df881 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -387,16 +387,16 @@ 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;
}
diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
index f757f87..ed05cae 100644
--- a/fs/autofs4/waitq.c
+++ b/fs/autofs4/waitq.c
@@ -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)
+ 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);