[PATCH v5 12/14] ecryptfs: use new start_creating/start_removing APIs

NeilBrown
2025-11-06T00:56:46Z

From: NeilBrown <neil@brown.name>

This requires the addition of start_creating_dentry() which is given the
dentry which has already been found, and asks for it to be locked and
its parent validated.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: NeilBrown <neil@brown.name>

---
changes since v4
- two places in ecryptfs uses dget_parent(dentry->d_parent),
thus incorrectly. getting grandparent. Changed to
dget_parent(dentry).
---
fs/ecryptfs/inode.c | 153 ++++++++++++++++++++----------------------
fs/namei.c | 33 +++++++++
include/linux/namei.h | 2 +
3 files changed, 107 insertions(+), 81 deletions(-)

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index fc6d37419753..37d6293600c7 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -24,18 +24,26 @@
#include <linux/unaligned.h>
#include "ecryptfs_kernel.h"

-static int lock_parent(struct dentry *dentry,
- struct dentry **lower_dentry,
- struct inode **lower_dir)
+static struct dentry *ecryptfs_start_creating_dentry(struct dentry *dentry)
{
- struct dentry *lower_dir_dentry;
+ struct dentry *parent = dget_parent(dentry);
+ struct dentry *ret;

- lower_dir_dentry = ecryptfs_dentry_to_lower(dentry->d_parent);
- *lower_dir = d_inode(lower_dir_dentry);
- *lower_dentry = ecryptfs_dentry_to_lower(dentry);
+ ret = start_creating_dentry(ecryptfs_dentry_to_lower(parent),
+ ecryptfs_dentry_to_lower(dentry));
+ dput(parent);
+ return ret;
+}

- inode_lock_nested(*lower_dir, I_MUTEX_PARENT);
- return (*lower_dentry)->d_parent == lower_dir_dentry ? 0 : -EINVAL;
+static struct dentry *ecryptfs_start_removing_dentry(struct dentry *dentry)
+{
+ struct dentry *parent = dget_parent(dentry);
+ struct dentry *ret;
+
+ ret = start_removing_dentry(ecryptfs_dentry_to_lower(parent),
+ ecryptfs_dentry_to_lower(dentry));
+ dput(parent);
+ return ret;
}

static int ecryptfs_inode_test(struct inode *inode, void *lower_inode)
@@ -141,15 +149,12 @@ static int ecryptfs_do_unlink(struct inode *dir, struct dentry *dentry,
struct inode *lower_dir;
int rc;

- rc = lock_parent(dentry, &lower_dentry, &lower_dir);
- dget(lower_dentry); // don't even try to make the lower negative
- if (!rc) {
- if (d_unhashed(lower_dentry))
- rc = -EINVAL;
- else
- rc = vfs_unlink(&nop_mnt_idmap, lower_dir, lower_dentry,
- NULL);
- }
+ lower_dentry = ecryptfs_start_removing_dentry(dentry);
+ if (IS_ERR(lower_dentry))
+ return PTR_ERR(lower_dentry);
+
+ lower_dir = lower_dentry->d_parent->d_inode;
+ rc = vfs_unlink(&nop_mnt_idmap, lower_dir, lower_dentry, NULL);
if (rc) {
printk(KERN_ERR "Error in vfs_unlink; rc = [%d]\n", rc);
goto out_unlock;
@@ -158,8 +163,7 @@ static int ecryptfs_do_unlink(struct inode *dir, struct dentry *dentry,
set_nlink(inode, ecryptfs_inode_to_lower(inode)->i_nlink);
inode_set_ctime_to_ts(inode, inode_get_ctime(dir));
out_unlock:
- dput(lower_dentry);
- inode_unlock(lower_dir);
+ end_removing(lower_dentry);
if (!rc)
d_drop(dentry);
return rc;
@@ -186,10 +190,12 @@ ecryptfs_do_create(struct inode *directory_inode,
struct inode *lower_dir;
struct inode *inode;

- rc = lock_parent(ecryptfs_dentry, &lower_dentry, &lower_dir);
- if (!rc)
- rc = vfs_create(&nop_mnt_idmap, lower_dir,
- lower_dentry, mode, true);
+ lower_dentry = ecryptfs_start_creating_dentry(ecryptfs_dentry);
+ if (IS_ERR(lower_dentry))
+ return ERR_CAST(lower_dentry);
+ lower_dir = lower_dentry->d_parent->d_inode;
+ rc = vfs_create(&nop_mnt_idmap, lower_dir,
+ lower_dentry, mode, true);
if (rc) {
printk(KERN_ERR "%s: Failure to create dentry in lower fs; "
"rc = [%d]\n", __func__, rc);
@@ -205,7 +211,7 @@ ecryptfs_do_create(struct inode *directory_inode,
fsstack_copy_attr_times(directory_inode, lower_dir);
fsstack_copy_inode_size(directory_inode, lower_dir);
out_lock:
- inode_unlock(lower_dir);
+ end_creating(lower_dentry, NULL);
return inode;
}

@@ -433,10 +439,12 @@ static int ecryptfs_link(struct dentry *old_dentry, struct inode *dir,

file_size_save = i_size_read(d_inode(old_dentry));
lower_old_dentry = ecryptfs_dentry_to_lower(old_dentry);
- rc = lock_parent(new_dentry, &lower_new_dentry, &lower_dir);
- if (!rc)
- rc = vfs_link(lower_old_dentry, &nop_mnt_idmap, lower_dir,
- lower_new_dentry, NULL);
+ lower_new_dentry = ecryptfs_start_creating_dentry(new_dentry);
+ if (IS_ERR(lower_new_dentry))
+ return PTR_ERR(lower_new_dentry);
+ lower_dir = lower_new_dentry->d_parent->d_inode;
+ rc = vfs_link(lower_old_dentry, &nop_mnt_idmap, lower_dir,
+ lower_new_dentry, NULL);
if (rc || d_really_is_negative(lower_new_dentry))
goto out_lock;
rc = ecryptfs_interpose(lower_new_dentry, new_dentry, dir->i_sb);
@@ -448,7 +456,7 @@ static int ecryptfs_link(struct dentry *old_dentry, struct inode *dir,
ecryptfs_inode_to_lower(d_inode(old_dentry))->i_nlink);
i_size_write(d_inode(new_dentry), file_size_save);
out_lock:
- inode_unlock(lower_dir);
+ end_creating(lower_new_dentry, NULL);
return rc;
}

@@ -468,9 +476,11 @@ static int ecryptfs_symlink(struct mnt_idmap *idmap,
size_t encoded_symlen;
struct ecryptfs_mount_crypt_stat *mount_crypt_stat = NULL;

- rc = lock_parent(dentry, &lower_dentry, &lower_dir);
- if (rc)
- goto out_lock;
+ lower_dentry = ecryptfs_start_creating_dentry(dentry);
+ if (IS_ERR(lower_dentry))
+ return PTR_ERR(lower_dentry);
+ lower_dir = lower_dentry->d_parent->d_inode;
+
mount_crypt_stat = &ecryptfs_superblock_to_private(
dir->i_sb)->mount_crypt_stat;
rc = ecryptfs_encrypt_and_encode_filename(&encoded_symname,
@@ -490,7 +500,7 @@ static int ecryptfs_symlink(struct mnt_idmap *idmap,
fsstack_copy_attr_times(dir, lower_dir);
fsstack_copy_inode_size(dir, lower_dir);
out_lock:
- inode_unlock(lower_dir);
+ end_creating(lower_dentry, NULL);
if (d_really_is_negative(dentry))
d_drop(dentry);
return rc;
@@ -501,12 +511,14 @@ static struct dentry *ecryptfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
{
int rc;
struct dentry *lower_dentry;
+ struct dentry *lower_dir_dentry;
struct inode *lower_dir;

- rc = lock_parent(dentry, &lower_dentry, &lower_dir);
- if (rc)
- goto out;
-
+ lower_dentry = ecryptfs_start_creating_dentry(dentry);
+ if (IS_ERR(lower_dentry))
+ return lower_dentry;
+ lower_dir_dentry = dget(lower_dentry->d_parent);
+ lower_dir = lower_dir_dentry->d_inode;
lower_dentry = vfs_mkdir(&nop_mnt_idmap, lower_dir,
lower_dentry, mode);
rc = PTR_ERR(lower_dentry);
@@ -522,7 +534,7 @@ static struct dentry *ecryptfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
fsstack_copy_inode_size(dir, lower_dir);
set_nlink(dir, lower_dir->i_nlink);
out:
- inode_unlock(lower_dir);
+ end_creating(lower_dentry, lower_dir_dentry);
if (d_really_is_negative(dentry))
d_drop(dentry);
return ERR_PTR(rc);
@@ -534,21 +546,18 @@ static int ecryptfs_rmdir(struct inode *dir, struct dentry *dentry)
struct inode *lower_dir;
int rc;

- rc = lock_parent(dentry, &lower_dentry, &lower_dir);
- dget(lower_dentry); // don't even try to make the lower negative
- if (!rc) {
- if (d_unhashed(lower_dentry))
- rc = -EINVAL;
- else
- rc = vfs_rmdir(&nop_mnt_idmap, lower_dir, lower_dentry);
- }
+ lower_dentry = ecryptfs_start_removing_dentry(dentry);
+ if (IS_ERR(lower_dentry))
+ return PTR_ERR(lower_dentry);
+ lower_dir = lower_dentry->d_parent->d_inode;
+
+ rc = vfs_rmdir(&nop_mnt_idmap, lower_dir, lower_dentry);
if (!rc) {
clear_nlink(d_inode(dentry));
fsstack_copy_attr_times(dir, lower_dir);
set_nlink(dir, lower_dir->i_nlink);
}
- dput(lower_dentry);
- inode_unlock(lower_dir);
+ end_removing(lower_dentry);
if (!rc)
d_drop(dentry);
return rc;
@@ -562,10 +571,12 @@ ecryptfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *lower_dentry;
struct inode *lower_dir;

- rc = lock_parent(dentry, &lower_dentry, &lower_dir);
- if (!rc)
- rc = vfs_mknod(&nop_mnt_idmap, lower_dir,
- lower_dentry, mode, dev);
+ lower_dentry = ecryptfs_start_creating_dentry(dentry);
+ if (IS_ERR(lower_dentry))
+ return PTR_ERR(lower_dentry);
+ lower_dir = lower_dentry->d_parent->d_inode;
+
+ rc = vfs_mknod(&nop_mnt_idmap, lower_dir, lower_dentry, mode, dev);
if (rc || d_really_is_negative(lower_dentry))
goto out;
rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb);
@@ -574,7 +585,7 @@ ecryptfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
fsstack_copy_attr_times(dir, lower_dir);
fsstack_copy_inode_size(dir, lower_dir);
out:
- inode_unlock(lower_dir);
+ end_removing(lower_dentry);
if (d_really_is_negative(dentry))
d_drop(dentry);
return rc;
@@ -590,7 +601,6 @@ ecryptfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
struct dentry *lower_new_dentry;
struct dentry *lower_old_dir_dentry;
struct dentry *lower_new_dir_dentry;
- struct dentry *trap;
struct inode *target_inode;
struct renamedata rd = {};

@@ -605,31 +615,13 @@ ecryptfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,

target_inode = d_inode(new_dentry);

- trap = lock_rename(lower_old_dir_dentry, lower_new_dir_dentry);
- if (IS_ERR(trap))
- return PTR_ERR(trap);
- dget(lower_new_dentry);
- rc = -EINVAL;
- if (lower_old_dentry->d_parent != lower_old_dir_dentry)
- goto out_lock;
- if (lower_new_dentry->d_parent != lower_new_dir_dentry)
- goto out_lock;
- if (d_unhashed(lower_old_dentry) || d_unhashed(lower_new_dentry))
- goto out_lock;
- /* source should not be ancestor of target */
- if (trap == lower_old_dentry)
- goto out_lock;
- /* target should not be ancestor of source */
- if (trap == lower_new_dentry) {
- rc = -ENOTEMPTY;
- goto out_lock;
- }
+ rd.mnt_idmap = &nop_mnt_idmap;
+ rd.old_parent = lower_old_dir_dentry;
+ rd.new_parent = lower_new_dir_dentry;
+ rc = start_renaming_two_dentries(&rd, lower_old_dentry, lower_new_dentry);
+ if (rc)
+ return rc;

- rd.mnt_idmap = &nop_mnt_idmap;
- rd.old_parent = lower_old_dir_dentry;
- rd.old_dentry = lower_old_dentry;
- rd.new_parent = lower_new_dir_dentry;
- rd.new_dentry = lower_new_dentry;
rc = vfs_rename(&rd);
if (rc)
goto out_lock;
@@ -640,8 +632,7 @@ ecryptfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
if (new_dir != old_dir)
fsstack_copy_attr_all(old_dir, d_inode(lower_old_dir_dentry));
out_lock:
- dput(lower_new_dentry);
- unlock_rename(lower_old_dir_dentry, lower_new_dir_dentry);
+ end_renaming(&rd);
return rc;
}

diff --git a/fs/namei.c b/fs/namei.c
index 7f0384ceb976..2444c7ddb926 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3397,6 +3397,39 @@ struct dentry *start_removing_noperm(struct dentry *parent,
}
EXPORT_SYMBOL(start_removing_noperm);

+/**
+ * start_creating_dentry - prepare to create a given dentry
+ * @parent: directory from which dentry should be removed
+ * @child: the dentry to be removed
+ *
+ * A lock is taken to protect the dentry again other dirops and
+ * the validity of the dentry is checked: correct parent and still hashed.
+ *
+ * If the dentry is valid and negative a reference is taken and
+ * returned. If not an error is returned.
+ *
+ * end_creating() should be called when creation is complete, or aborted.
+ *
+ * Returns: the valid dentry, or an error.
+ */
+struct dentry *start_creating_dentry(struct dentry *parent,
+ struct dentry *child)
+{
+ inode_lock_nested(parent->d_inode, I_MUTEX_PARENT);
+ if (unlikely(IS_DEADDIR(parent->d_inode) ||
+ child->d_parent != parent ||
+ d_unhashed(child))) {
+ inode_unlock(parent->d_inode);
+ return ERR_PTR(-EINVAL);
+ }
+ if (d_is_positive(child)) {
+ inode_unlock(parent->d_inode);
+ return ERR_PTR(-EEXIST);
+ }
+ return dget(child);
+}
+EXPORT_SYMBOL(start_creating_dentry);
+
/**
* start_removing_dentry - prepare to remove a given dentry
* @parent: directory from which dentry should be removed
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 9104c7104191..0e6b1b9afc26 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -101,6 +101,8 @@ struct dentry *start_removing_killable(struct mnt_idmap *idmap,
struct qstr *name);
struct dentry *start_creating_noperm(struct dentry *parent, struct qstr *name);
struct dentry *start_removing_noperm(struct dentry *parent, struct qstr *name);
+struct dentry *start_creating_dentry(struct dentry *parent,
+ struct dentry *child);
struct dentry *start_removing_dentry(struct dentry *parent,
struct dentry *child);

--
2.50.0.107.gf914562f5916.dirty