[PATCH 05/11] VFS: change kern_path_locked() and user_path_locked_at() to never return negative dentry

NeilBrown
2024-12-20T03:09:12Z

No callers of kern_path_locked() or user_path_locked_at() want a
negative dentry. So change them to return -ENOENT instead. This
simplifies callers.

This results in a subtle change to bcachefs in that an ioctl will now
return -ENOENT in preference to -EXDEV. I believe this restores the
behaviour to what it was prior to
Commit bbe6a7c899e7 ("bch2_ioctl_subvolume_destroy(): fix locking")

Signed-off-by: NeilBrown <neilb@suse.de>
---
drivers/base/devtmpfs.c | 65 +++++++++++++++++++----------------------
fs/bcachefs/fs-ioctl.c | 4 ---
fs/namei.c | 4 +++
kernel/audit_watch.c | 12 ++++----
4 files changed, 40 insertions(+), 45 deletions(-)

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index b848764ef018..c9e34842139f 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -245,15 +245,12 @@ static int dev_rmdir(const char *name)
dentry = kern_path_locked(name, &parent);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
- if (d_really_is_positive(dentry)) {
- if (d_inode(dentry)->i_private == &thread)
- err = vfs_rmdir(&nop_mnt_idmap, d_inode(parent.dentry),
- dentry);
- else
- err = -EPERM;
- } else {
- err = -ENOENT;
- }
+ if (d_inode(dentry)->i_private == &thread)
+ err = vfs_rmdir(&nop_mnt_idmap, d_inode(parent.dentry),
+ dentry);
+ else
+ err = -EPERM;
+
dput(dentry);
inode_unlock(d_inode(parent.dentry));
path_put(&parent);
@@ -310,6 +307,8 @@ static int handle_remove(const char *nodename, struct device *dev)
{
struct path parent;
struct dentry *dentry;
+ struct kstat stat;
+ struct path p;
int deleted = 0;
int err;

@@ -317,32 +316,28 @@ static int handle_remove(const char *nodename, struct device *dev)
if (IS_ERR(dentry))
return PTR_ERR(dentry);

- if (d_really_is_positive(dentry)) {
- struct kstat stat;
- struct path p = {.mnt = parent.mnt, .dentry = dentry};
- err = vfs_getattr(&p, &stat, STATX_TYPE | STATX_MODE,
- AT_STATX_SYNC_AS_STAT);
- if (!err && dev_mynode(dev, d_inode(dentry), &stat)) {
- struct iattr newattrs;
- /*
- * before unlinking this node, reset permissions
- * of possible references like hardlinks
- */
- newattrs.ia_uid = GLOBAL_ROOT_UID;
- newattrs.ia_gid = GLOBAL_ROOT_GID;
- newattrs.ia_mode = stat.mode & ~0777;
- newattrs.ia_valid =
- ATTR_UID|ATTR_GID|ATTR_MODE;
- inode_lock(d_inode(dentry));
- notify_change(&nop_mnt_idmap, dentry, &newattrs, NULL);
- inode_unlock(d_inode(dentry));
- err = vfs_unlink(&nop_mnt_idmap, d_inode(parent.dentry),
- dentry, NULL);
- if (!err || err == -ENOENT)
- deleted = 1;
- }
- } else {
- err = -ENOENT;
+ p.mnt = parent.mnt;
+ p.dentry = dentry;
+ err = vfs_getattr(&p, &stat, STATX_TYPE | STATX_MODE,
+ AT_STATX_SYNC_AS_STAT);
+ if (!err && dev_mynode(dev, d_inode(dentry), &stat)) {
+ struct iattr newattrs;
+ /*
+ * before unlinking this node, reset permissions
+ * of possible references like hardlinks
+ */
+ newattrs.ia_uid = GLOBAL_ROOT_UID;
+ newattrs.ia_gid = GLOBAL_ROOT_GID;
+ newattrs.ia_mode = stat.mode & ~0777;
+ newattrs.ia_valid =
+ ATTR_UID|ATTR_GID|ATTR_MODE;
+ inode_lock(d_inode(dentry));
+ notify_change(&nop_mnt_idmap, dentry, &newattrs, NULL);
+ inode_unlock(d_inode(dentry));
+ err = vfs_unlink(&nop_mnt_idmap, d_inode(parent.dentry),
+ dentry, NULL);
+ if (!err || err == -ENOENT)
+ deleted = 1;
}
dput(dentry);
inode_unlock(d_inode(parent.dentry));
diff --git a/fs/bcachefs/fs-ioctl.c b/fs/bcachefs/fs-ioctl.c
index 405cf08bda34..c5464219b23f 100644
--- a/fs/bcachefs/fs-ioctl.c
+++ b/fs/bcachefs/fs-ioctl.c
@@ -516,10 +516,6 @@ static long bch2_ioctl_subvolume_destroy(struct bch_fs *c, struct file *filp,
ret = -EXDEV;
goto err;
}
- if (!d_is_positive(victim)) {
- ret = -ENOENT;
- goto err;
- }
ret = __bch2_unlink(dir, victim, true);
if (!ret) {
fsnotify_rmdir(dir, victim);
diff --git a/fs/namei.c b/fs/namei.c
index 395bfbc8fc92..8780406cb4d7 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2743,6 +2743,10 @@ static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct
}
inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
d = lookup_one_qstr_excl(&last, path->dentry, 0);
+ if (!IS_ERR(d) && d_is_negative(d)) {
+ dput(d);
+ d = ERR_PTR(-ENOENT);
+ }
if (IS_ERR(d)) {
inode_unlock(path->dentry->d_inode);
path_put(path);
diff --git a/kernel/audit_watch.c b/kernel/audit_watch.c
index 7f358740e958..e3130675ee6b 100644
--- a/kernel/audit_watch.c
+++ b/kernel/audit_watch.c
@@ -350,11 +350,10 @@ static int audit_get_nd(struct audit_watch *watch, struct path *parent)
struct dentry *d = kern_path_locked(watch->path, parent);
if (IS_ERR(d))
return PTR_ERR(d);
- if (d_is_positive(d)) {
- /* update watch filter fields */
- watch->dev = d->d_sb->s_dev;
- watch->ino = d_backing_inode(d)->i_ino;
- }
+ /* update watch filter fields */
+ watch->dev = d->d_sb->s_dev;
+ watch->ino = d_backing_inode(d)->i_ino;
+
inode_unlock(d_backing_inode(parent->dentry));
dput(d);
return 0;
@@ -419,7 +418,7 @@ int audit_add_watch(struct audit_krule *krule, struct list_head **list)
/* caller expects mutex locked */
mutex_lock(&audit_filter_mutex);

- if (ret) {
+ if (ret && ret != -ENOENT) {
audit_put_watch(watch);
return ret;
}
@@ -438,6 +437,7 @@ int audit_add_watch(struct audit_krule *krule, struct list_head **list)

h = audit_hash_ino((u32)watch->ino);
*list = &audit_inode_hash[h];
+ ret = 0;
error:
path_put(&parent_path);
audit_put_watch(watch);
--
2.47.0