diff options
| author | Christian Brauner <brauner@kernel.org> | 2026-06-15 15:19:52 +0200 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2026-06-29 10:32:31 +0200 |
| commit | 10a16f5b9111da6e553f8533605f7216e13a37b8 (patch) | |
| tree | fe5707bac2b260cf86159e7fbdf79ad751e0b052 /fs | |
| parent | 21b9aa3b8025445a71d5715458ea88457ca9e43f (diff) | |
ovl: handle idmapped mounts in ovl_setattr()
Pass the mount's struct mnt_idmap to setattr_prepare() so that the
permission checks for a chown/chmod performed through an idmapped
overlay mount are evaluated in the mount's id space.
The ownership requested in @attr is expressed relative to the overlay
mount idmap. Before forwarding the change to the upper layer via
ovl_do_notify_change() - whose notify_change() applies the upper layer
idmap in turn - rebase ia_vfsuid/ia_vfsgid into the overlay's own id
space, i.e. the same space as the overlay inode's i_{u,g}id established
by ovl_copyattr(). Without this rebase the upper layer would interpret
the caller's mount-relative id as an upper-relative one and store the
wrong owner on disk, or reject it with -EOVERFLOW.
from_vfsuid() returns INVALID_UID for an id that the overlay mount
idmap does not map; that invalid id is carried faithfully into the
forwarded iattr and rejected by the upper notify_change() via
vfsuid_has_fsmapping(), so no bogus owner can be written.
No functional change until FS_ALLOW_IDMAP is set on ovl_fs_type; until
then the overlay mount idmap is &nop_mnt_idmap and from_vfsuid() is the
identity.
Link: https://patch.msgid.link/20260615-work-idmapped-overlayfs-v1-3-7381632aa402@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/overlayfs/inode.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index f59db57dfd55..33734ca971e1 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -26,10 +26,18 @@ int ovl_setattr(struct mnt_idmap *idmap, struct dentry *dentry, bool full_copy_up = false; struct dentry *upperdentry; - err = setattr_prepare(&nop_mnt_idmap, dentry, attr); + err = setattr_prepare(idmap, dentry, attr); if (err) return err; + /* Rebase ownership from the mount idmap into overlay id space. */ + if (attr->ia_valid & ATTR_UID) + attr->ia_vfsuid = VFSUIDT_INIT(from_vfsuid(idmap, + i_user_ns(d_inode(dentry)), attr->ia_vfsuid)); + if (attr->ia_valid & ATTR_GID) + attr->ia_vfsgid = VFSGIDT_INIT(from_vfsgid(idmap, + i_user_ns(d_inode(dentry)), attr->ia_vfsgid)); + if (attr->ia_valid & ATTR_SIZE) { /* Truncate should trigger data copy up as well */ full_copy_up = true; |