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fs: port privilege checking helpers to mnt_idmap

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Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2023-01-13 12:49:27 +01:00 • committed by Christian Brauner (Microsoft)
parent 01beba7957
commit 9452e93e6d
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GPG key ID: 91C61BC06578DCA2
20 changed files with 93 additions and 94 deletions
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5
fs/open.c
View file

@ -39,7 +39,6 @@
int do_truncate(struct mnt_idmap *idmap, struct dentry *dentry,
loff_t length, unsigned int time_attrs, struct file *filp)
{
struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
int ret;
struct iattr newattrs;
@ -55,7 +54,7 @@ int do_truncate(struct mnt_idmap *idmap, struct dentry *dentry,
}
/* Remove suid, sgid, and file capabilities on truncate too */
ret = dentry_needs_remove_privs(mnt_userns, dentry);
ret = dentry_needs_remove_privs(idmap, dentry);
if (ret < 0)
return ret;
if (ret)
@ -729,7 +728,7 @@ retry_deleg:
inode_lock(inode);
if (!S_ISDIR(inode->i_mode))
newattrs.ia_valid |= ATTR_KILL_SUID | ATTR_KILL_PRIV |
setattr_should_drop_sgid(mnt_userns, inode);
setattr_should_drop_sgid(idmap, inode);
/* Continue to send actual fs values, not the mount values. */
error = security_path_chown(
path,