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VFS: change kern_path_locked() and user_path_locked_at() to never return negative dentry

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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 bbe6a7c899 ("bch2_ioctl_subvolume_destroy(): fix locking")

Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20250217003020.3170652-2-neilb@suse.de
Acked-by: Paul Moore <paul@paul-moore.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
NeilBrown 2025-02-17 11:27:20 +11:00 committed by Christian Brauner
parent 2c3230fb8d
commit 1c3cb50b58
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GPG key ID: 91C61BC06578DCA2
5 changed files with 48 additions and 45 deletions
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8
Documentation/filesystems/porting.rst
View file

@ -1157,3 +1157,11 @@ in normal case it points into the pathname being looked up.
NOTE: if you need something like full path from the root of filesystem,
you are still on your own - this assists with simple cases, but it's not
magic.
---
** recommended**
kern_path_locked() and user_path_locked() no longer return a negative
dentry so this doesn't need to be checked. If the name cannot be found,
ERR_PTR(-ENOENT) is returned.

65
drivers/base/devtmpfs.c
View file

@ -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));

4
fs/bcachefs/fs-ioctl.c
View file

@ -511,10 +511,6 @@ 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);

4
fs/namei.c
View file

@ -2741,6 +2741,10 @@ 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);

12
kernel/audit_watch.c
View file

@ -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;
@ -419,10 +418,11 @@ 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;
}
ret = 0;
/* either find an old parent or attach a new one */
parent = audit_find_parent(d_backing_inode(parent_path.dentry));