github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-09-23 21:48:54 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

ovl: handle idmapped mounts in ovl_setattr()

Browse Source 
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>
This commit is contained in:
Christian Brauner 2026-06-15 15:19:52 +02:00
parent 21b9aa3b80
commit 10a16f5b91
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
1 changed files with 9 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
fs/overlayfs/inode.c
View File

@ -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;