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.
Signed-off-by: Ian Kent <raven@xxxxxxxxxx>
---
fs/autofs4/dev-ioctl.c | 72 +++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 62 insertions(+), 10 deletions(-)
diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index 743c7c2..1d24e42 100644
--- a/fs/autofs4/dev-ioctl.c
+++ b/fs/autofs4/dev-ioctl.c
@@ -183,13 +183,67 @@ static int autofs_dev_ioctl_protosubver(struct file *fp,
return 0;
}
+/*
+ * Lookup the the topmost path of a (possible) mount stack.
+ *
+ * kern_path() can't be used here because the caller might not
+ * "own" the automount dentry yet and we would end up calling
+ * back to ourself.
+ */
+static int kern_path_top(const char *pathname,
+ unsigned int flags, struct path *path)
+{
+ struct dentry *dentry;
+ struct qstr name;
+ const char *tmp;
+ unsigned int len;
+ int err;
+
+ len = strlen(pathname);
+ if (len <= 1)
+ return -EINVAL;
+
+ tmp = pathname + len - 1;
+ len = 0;
+ if (*tmp == '/')
+ tmp--;
+ do {
+ if (*tmp == '/')
+ break;
+ len++;
+ } while (--tmp >= pathname);
+ tmp++;
+
+ err = kern_path(pathname, flags | LOOKUP_PARENT, path);
+ if (err)
+ return err;
+
+ name.name = tmp;
+ name.len = len;
+ name.hash = full_name_hash(tmp, len);
+
+ dentry = d_lookup(path->dentry, &name);
+ if (!dentry) {
+ path_put(path);
+ return -ENOENT;
+ }
+ dput(path->dentry);
+ path->dentry = dentry;
+
+ while (follow_down_one(path))
+ ;
+
+ 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_top(pathname, 0, &path);
if (err)
return err;
err = -ENOENT;
@@ -197,10 +251,9 @@ 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 +539,11 @@ 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.
@@ -519,7 +571,7 @@ 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_top(name, LOOKUP_FOLLOW, &path);
else
err = find_autofs_mount(name, &path, test_by_type, &type);
if (err)
--
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