[PATCH v2 06/10] fs: use low-level mapping helpers

Christian Brauner
2021-11-30T12:11:10Z

In a few places the vfs needs to interact with bare k{g,u}ids directly
instead of struct inode. These are just a few. In previous patches we
introduced low-level mapping helpers that are able to support
filesystems mounted an idmapping. This patch simply converts the places
to use these new helpers.

Link: https://lore.kernel.org/r/20211123114227.3124056-7-brauner@kernel.org (v1)
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
CC: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v2 */
unchanged
---
fs/ksmbd/smbacl.c | 18 ++----------------
fs/ksmbd/smbacl.h | 4 ++--
fs/open.c | 4 ++--
fs/posix_acl.c | 16 ++++++++++------
security/commoncap.c | 13 ++++++++-----
5 files changed, 24 insertions(+), 31 deletions(-)

diff --git a/fs/ksmbd/smbacl.c b/fs/ksmbd/smbacl.c
index ab8099e0fd7f..6ecf55ea1fed 100644
--- a/fs/ksmbd/smbacl.c
+++ b/fs/ksmbd/smbacl.c
@@ -275,14 +275,7 @@ static int sid_to_id(struct user_namespace *user_ns,
uid_t id;

id = le32_to_cpu(psid->sub_auth[psid->num_subauth - 1]);
- /*
- * Translate raw sid into kuid in the server's user
- * namespace.
- */
- uid = make_kuid(&init_user_ns, id);
-
- /* If this is an idmapped mount, apply the idmapping. */
- uid = kuid_from_mnt(user_ns, uid);
+ uid = mapped_kuid_user(user_ns, &init_user_ns, KUIDT_INIT(id));
if (uid_valid(uid)) {
fattr->cf_uid = uid;
rc = 0;
@@ -292,14 +285,7 @@ static int sid_to_id(struct user_namespace *user_ns,
gid_t id;

id = le32_to_cpu(psid->sub_auth[psid->num_subauth - 1]);
- /*
- * Translate raw sid into kgid in the server's user
- * namespace.
- */
- gid = make_kgid(&init_user_ns, id);
-
- /* If this is an idmapped mount, apply the idmapping. */
- gid = kgid_from_mnt(user_ns, gid);
+ gid = mapped_kgid_user(user_ns, &init_user_ns, KGIDT_INIT(id));
if (gid_valid(gid)) {
fattr->cf_gid = gid;
rc = 0;
diff --git a/fs/ksmbd/smbacl.h b/fs/ksmbd/smbacl.h
index eba1ebb9e92e..811af3309429 100644
--- a/fs/ksmbd/smbacl.h
+++ b/fs/ksmbd/smbacl.h
@@ -217,7 +217,7 @@ static inline uid_t posix_acl_uid_translate(struct user_namespace *mnt_userns,
kuid_t kuid;

/* If this is an idmapped mount, apply the idmapping. */
- kuid = kuid_into_mnt(mnt_userns, pace->e_uid);
+ kuid = mapped_kuid_fs(mnt_userns, &init_user_ns, pace->e_uid);

/* Translate the kuid into a userspace id ksmbd would see. */
return from_kuid(&init_user_ns, kuid);
@@ -229,7 +229,7 @@ static inline gid_t posix_acl_gid_translate(struct user_namespace *mnt_userns,
kgid_t kgid;

/* If this is an idmapped mount, apply the idmapping. */
- kgid = kgid_into_mnt(mnt_userns, pace->e_gid);
+ kgid = mapped_kgid_fs(mnt_userns, &init_user_ns, pace->e_gid);

/* Translate the kgid into a userspace id ksmbd would see. */
return from_kgid(&init_user_ns, kgid);
diff --git a/fs/open.c b/fs/open.c
index 2450cc1a2f64..40a00e71865b 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -653,8 +653,8 @@ int chown_common(const struct path *path, uid_t user, gid_t group)
gid = make_kgid(current_user_ns(), group);

mnt_userns = mnt_user_ns(path->mnt);
- uid = kuid_from_mnt(mnt_userns, uid);
- gid = kgid_from_mnt(mnt_userns, gid);
+ uid = mapped_kuid_user(mnt_userns, &init_user_ns, uid);
+ gid = mapped_kgid_user(mnt_userns, &init_user_ns, gid);

retry_deleg:
newattrs.ia_valid = ATTR_CTIME;
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 632bfdcf7cc0..4b5fb9a9b90f 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -375,7 +375,9 @@ posix_acl_permission(struct user_namespace *mnt_userns, struct inode *inode,
goto check_perm;
break;
case ACL_USER:
- uid = kuid_into_mnt(mnt_userns, pa->e_uid);
+ uid = mapped_kuid_fs(mnt_userns,
+ &init_user_ns,
+ pa->e_uid);
if (uid_eq(uid, current_fsuid()))
goto mask;
break;
@@ -388,7 +390,9 @@ posix_acl_permission(struct user_namespace *mnt_userns, struct inode *inode,
}
break;
case ACL_GROUP:
- gid = kgid_into_mnt(mnt_userns, pa->e_gid);
+ gid = mapped_kgid_fs(mnt_userns,
+ &init_user_ns,
+ pa->e_gid);
if (in_group_p(gid)) {
found = 1;
if ((pa->e_perm & want) == want)
@@ -735,17 +739,17 @@ static void posix_acl_fix_xattr_userns(
case ACL_USER:
uid = make_kuid(from, le32_to_cpu(entry->e_id));
if (from_user)
- uid = kuid_from_mnt(mnt_userns, uid);
+ uid = mapped_kuid_user(mnt_userns, &init_user_ns, uid);
else
- uid = kuid_into_mnt(mnt_userns, uid);
+ uid = mapped_kuid_fs(mnt_userns, &init_user_ns, uid);
entry->e_id = cpu_to_le32(from_kuid(to, uid));
break;
case ACL_GROUP:
gid = make_kgid(from, le32_to_cpu(entry->e_id));
if (from_user)
- gid = kgid_from_mnt(mnt_userns, gid);
+ gid = mapped_kgid_user(mnt_userns, &init_user_ns, gid);
else
- gid = kgid_into_mnt(mnt_userns, gid);
+ gid = mapped_kgid_fs(mnt_userns, &init_user_ns, gid);
entry->e_id = cpu_to_le32(from_kgid(to, gid));
break;
default:
diff --git a/security/commoncap.c b/security/commoncap.c
index 09479f71ee2e..d288a62e2999 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -419,7 +419,7 @@ int cap_inode_getsecurity(struct user_namespace *mnt_userns,
kroot = make_kuid(fs_ns, root);

/* If this is an idmapped mount shift the kuid. */
- kroot = kuid_into_mnt(mnt_userns, kroot);
+ kroot = mapped_kuid_fs(mnt_userns, &init_user_ns, kroot);

/* If the root kuid maps to a valid uid in current ns, then return
* this as a nscap. */
@@ -489,6 +489,7 @@ int cap_inode_getsecurity(struct user_namespace *mnt_userns,
* @size: size of @ivalue
* @task_ns: user namespace of the caller
* @mnt_userns: user namespace of the mount the inode was found from
+ * @fs_userns: user namespace of the filesystem
*
* If the inode has been found through an idmapped mount the user namespace of
* the vfsmount must be passed through @mnt_userns. This function will then
@@ -498,7 +499,8 @@ int cap_inode_getsecurity(struct user_namespace *mnt_userns,
*/
static kuid_t rootid_from_xattr(const void *value, size_t size,
struct user_namespace *task_ns,
- struct user_namespace *mnt_userns)
+ struct user_namespace *mnt_userns,
+ struct user_namespace *fs_userns)
{
const struct vfs_ns_cap_data *nscap = value;
kuid_t rootkid;
@@ -508,7 +510,7 @@ static kuid_t rootid_from_xattr(const void *value, size_t size,
rootid = le32_to_cpu(nscap->rootid);

rootkid = make_kuid(task_ns, rootid);
- return kuid_from_mnt(mnt_userns, rootkid);
+ return mapped_kuid_user(mnt_userns, fs_userns, rootkid);
}

static bool validheader(size_t size, const struct vfs_cap_data *cap)
@@ -559,7 +561,8 @@ int cap_convert_nscap(struct user_namespace *mnt_userns, struct dentry *dentry,
/* user is privileged, just write the v2 */
return size;

- rootid = rootid_from_xattr(*ivalue, size, task_ns, mnt_userns);
+ rootid = rootid_from_xattr(*ivalue, size, task_ns, mnt_userns,
+ &init_user_ns);
if (!uid_valid(rootid))
return -EINVAL;

@@ -700,7 +703,7 @@ int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
/* Limit the caps to the mounter of the filesystem
* or the more limited uid specified in the xattr.
*/
- rootkuid = kuid_into_mnt(mnt_userns, rootkuid);
+ rootkuid = mapped_kuid_fs(mnt_userns, &init_user_ns, rootkuid);
if (!rootid_owns_currentns(rootkuid))
return -ENODATA;

--
2.30.2