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Message-ID: <20250206-brust-lernbegierde-217cbba91255@brauner>
Date: Thu, 6 Feb 2025 13:31:56 +0100
From: Christian Brauner <brauner@...nel.org>
To: NeilBrown <neilb@...e.de>
Cc: Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>,
Linus Torvalds <torvalds@...ux-foundation.org>, Jeff Layton <jlayton@...nel.org>,
Dave Chinner <david@...morbit.com>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/19] VFS: change kern_path_locked() and
user_path_locked_at() to never return negative dentry
On Thu, Feb 06, 2025 at 04:42:41PM +1100, NeilBrown wrote:
> 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@...e.de>
> ---
It would be nice if you could send this as a separate cleanup patch.
It seems unrelated to the series.
> 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 15725b4ce393..595b57fabc9a 100644
> --- a/fs/bcachefs/fs-ioctl.c
> +++ b/fs/bcachefs/fs-ioctl.c
> @@ -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);
> diff --git a/fs/namei.c b/fs/namei.c
> index d684102d873d..1901120bcbb8 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -2745,6 +2745,10 @@ 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(&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);
> --
> 2.47.1
>
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