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-rw-r--r--fs/afs/mntpt.c5
-rw-r--r--fs/autofs4/autofs_i.h13
-rw-r--r--fs/autofs4/dev-ioctl.c2
-rw-r--r--fs/autofs4/expire.c2
-rw-r--r--fs/autofs4/root.c11
-rw-r--r--fs/cifs/cifs_dfs_ref.c5
-rw-r--r--fs/namei.c72
-rw-r--r--fs/namespace.c14
-rw-r--r--fs/nfs/namespace.c5
-rw-r--r--fs/nfsd/vfs.c5
10 files changed, 91 insertions, 43 deletions
diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
index e83c0336e7b..f3e891d57a2 100644
--- a/fs/afs/mntpt.c
+++ b/fs/afs/mntpt.c
@@ -273,10 +273,7 @@ static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd)
break;
case -EBUSY:
/* someone else made a mount here whilst we were busy */
- while (d_mountpoint(nd->path.dentry) &&
- follow_down(&nd->path))
- ;
- err = 0;
+ err = follow_down(&nd->path, false);
default:
mntput(newmnt);
break;
diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index 0fffe1c24ce..eb67953452b 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -229,19 +229,6 @@ int autofs4_wait(struct autofs_sb_info *,struct dentry *, enum autofs_notify);
int autofs4_wait_release(struct autofs_sb_info *,autofs_wqt_t,int);
void autofs4_catatonic_mode(struct autofs_sb_info *);
-static inline int autofs4_follow_mount(struct path *path)
-{
- int res = 0;
-
- while (d_mountpoint(path->dentry)) {
- int followed = follow_down(path);
- if (!followed)
- break;
- res = 1;
- }
- return res;
-}
-
static inline u32 autofs4_get_dev(struct autofs_sb_info *sbi)
{
return new_encode_dev(sbi->sb->s_dev);
diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index eff9a419469..1442da4860e 100644
--- a/fs/autofs4/dev-ioctl.c
+++ b/fs/autofs4/dev-ioctl.c
@@ -551,7 +551,7 @@ static int autofs_dev_ioctl_ismountpoint(struct file *fp,
err = have_submounts(path.dentry);
- if (follow_down(&path))
+ if (follow_down_one(&path))
magic = path.mnt->mnt_sb->s_magic;
}
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index cc1d0136590..6a930b90d38 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -56,7 +56,7 @@ static int autofs4_mount_busy(struct vfsmount *mnt, struct dentry *dentry)
path_get(&path);
- if (!follow_down(&path))
+ if (!follow_down_one(&path))
goto done;
if (is_autofs4_dentry(path.dentry)) {
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 651e4ef563b..20225636a4e 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -234,7 +234,7 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
nd->flags);
/*
* For an expire of a covered direct or offset mount we need
- * to break out of follow_down() at the autofs mount trigger
+ * to break out of follow_down_one() at the autofs mount trigger
* (d_mounted--), so we can see the expiring flag, and manage
* the blocking and following here until the expire is completed.
*/
@@ -243,7 +243,7 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
if (ino->flags & AUTOFS_INF_EXPIRING) {
spin_unlock(&sbi->fs_lock);
/* Follow down to our covering mount. */
- if (!follow_down(&nd->path))
+ if (!follow_down_one(&nd->path))
goto done;
goto follow;
}
@@ -292,11 +292,10 @@ follow:
* multi-mount with no root offset so we don't need
* to follow it.
*/
- if (d_mountpoint(dentry)) {
- if (!autofs4_follow_mount(&nd->path)) {
- status = -ENOENT;
+ if (d_managed(dentry)) {
+ status = follow_down(&nd->path, false);
+ if (status < 0)
goto out_error;
- }
}
done:
diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
index c68a056f27f..83479cf63f9 100644
--- a/fs/cifs/cifs_dfs_ref.c
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -273,10 +273,7 @@ static int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
break;
case -EBUSY:
/* someone else made a mount here whilst we were busy */
- while (d_mountpoint(nd->path.dentry) &&
- follow_down(&nd->path))
- ;
- err = 0;
+ err = follow_down(&nd->path, false);
default:
mntput(newmnt);
break;
diff --git a/fs/namei.c b/fs/namei.c
index 16109da68bb..9d3033dc22e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -960,6 +960,7 @@ static int follow_automount(struct path *path, unsigned flags,
/*
* Handle a dentry that is managed in some way.
+ * - Flagged for transit management (autofs)
* - Flagged as mountpoint
* - Flagged as automount point
*
@@ -979,6 +980,16 @@ static int follow_managed(struct path *path, unsigned flags)
while (managed = ACCESS_ONCE(path->dentry->d_flags),
managed &= DCACHE_MANAGED_DENTRY,
unlikely(managed != 0)) {
+ /* Allow the filesystem to manage the transit without i_mutex
+ * being held. */
+ if (managed & DCACHE_MANAGE_TRANSIT) {
+ BUG_ON(!path->dentry->d_op);
+ BUG_ON(!path->dentry->d_op->d_manage);
+ ret = path->dentry->d_op->d_manage(path->dentry, false);
+ if (ret < 0)
+ return ret == -EISDIR ? 0 : ret;
+ }
+
/* Transit to a mounted filesystem. */
if (managed & DCACHE_MOUNTED) {
struct vfsmount *mounted = lookup_mnt(path);
@@ -1012,7 +1023,7 @@ static int follow_managed(struct path *path, unsigned flags)
return 0;
}
-int follow_down(struct path *path)
+int follow_down_one(struct path *path)
{
struct vfsmount *mounted;
@@ -1029,14 +1040,19 @@ int follow_down(struct path *path)
/*
* Skip to top of mountpoint pile in rcuwalk mode. We abort the rcu-walk if we
- * meet an automount point and we're not walking to "..". True is returned to
+ * meet a managed dentry and we're not walking to "..". True is returned to
* continue, false to abort.
*/
static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
struct inode **inode, bool reverse_transit)
{
+ unsigned abort_mask =
+ reverse_transit ? 0 : DCACHE_MANAGE_TRANSIT;
+
while (d_mountpoint(path->dentry)) {
struct vfsmount *mounted;
+ if (path->dentry->d_flags & abort_mask)
+ return true;
mounted = __lookup_mnt(path->mnt, path->dentry, 1);
if (!mounted)
break;
@@ -1087,6 +1103,57 @@ static int follow_dotdot_rcu(struct nameidata *nd)
}
/*
+ * Follow down to the covering mount currently visible to userspace. At each
+ * point, the filesystem owning that dentry may be queried as to whether the
+ * caller is permitted to proceed or not.
+ *
+ * Care must be taken as namespace_sem may be held (indicated by mounting_here
+ * being true).
+ */
+int follow_down(struct path *path, bool mounting_here)
+{
+ unsigned managed;
+ int ret;
+
+ while (managed = ACCESS_ONCE(path->dentry->d_flags),
+ unlikely(managed & DCACHE_MANAGED_DENTRY)) {
+ /* Allow the filesystem to manage the transit without i_mutex
+ * being held.
+ *
+ * We indicate to the filesystem if someone is trying to mount
+ * something here. This gives autofs the chance to deny anyone
+ * other than its daemon the right to mount on its
+ * superstructure.
+ *
+ * The filesystem may sleep at this point.
+ */
+ if (managed & DCACHE_MANAGE_TRANSIT) {
+ BUG_ON(!path->dentry->d_op);
+ BUG_ON(!path->dentry->d_op->d_manage);
+ ret = path->dentry->d_op->d_manage(path->dentry, mounting_here);
+ if (ret < 0)
+ return ret == -EISDIR ? 0 : ret;
+ }
+
+ /* Transit to a mounted filesystem. */
+ if (managed & DCACHE_MOUNTED) {
+ struct vfsmount *mounted = lookup_mnt(path);
+ if (!mounted)
+ break;
+ dput(path->dentry);
+ mntput(path->mnt);
+ path->mnt = mounted;
+ path->dentry = dget(mounted->mnt_root);
+ continue;
+ }
+
+ /* Don't handle automount points here */
+ break;
+ }
+ return 0;
+}
+
+/*
* Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
*/
static void follow_mount(struct path *path)
@@ -3530,6 +3597,7 @@ const struct inode_operations page_symlink_inode_operations = {
};
EXPORT_SYMBOL(user_path_at);
+EXPORT_SYMBOL(follow_down_one);
EXPORT_SYMBOL(follow_down);
EXPORT_SYMBOL(follow_up);
EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
diff --git a/fs/namespace.c b/fs/namespace.c
index 3ddfd9046c4..d94ccd6ddaf 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1844,9 +1844,10 @@ static int do_move_mount(struct path *path, char *old_name)
return err;
down_write(&namespace_sem);
- while (d_mountpoint(path->dentry) &&
- follow_down(path))
- ;
+ err = follow_down(path, true);
+ if (err < 0)
+ goto out;
+
err = -EINVAL;
if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))
goto out;
@@ -1940,9 +1941,10 @@ int do_add_mount(struct vfsmount *newmnt, struct path *path,
down_write(&namespace_sem);
/* Something was mounted here while we slept */
- while (d_mountpoint(path->dentry) &&
- follow_down(path))
- ;
+ err = follow_down(path, true);
+ if (err < 0)
+ goto unlock;
+
err = -EINVAL;
if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(path->mnt))
goto unlock;
diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index 74aaf3963c1..bfcb933e575 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -176,10 +176,7 @@ out_err:
path_put(&nd->path);
goto out;
out_follow:
- while (d_mountpoint(nd->path.dentry) &&
- follow_down(&nd->path))
- ;
- err = 0;
+ err = follow_down(&nd->path, false);
goto out;
}
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 230b79fbf00..0f79e33a65d 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -88,8 +88,9 @@ nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp,
.dentry = dget(dentry)};
int err = 0;
- while (d_mountpoint(path.dentry) && follow_down(&path))
- ;
+ err = follow_down(&path, false);
+ if (err < 0)
+ goto out;
exp2 = rqst_exp_get_by_name(rqstp, &path);
if (IS_ERR(exp2)) {
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2024-12-02 09:18:40 +0000