diff mbox series

[v6,16/40] open: handle idmapped mounts

Message ID 20210121131959.646623-17-christian.brauner@ubuntu.com (mailing list archive)
State New
Headers show
Series idmapped mounts | expand

Commit Message

Christian Brauner Jan. 21, 2021, 1:19 p.m. UTC
For core file operations such as changing directories or chrooting,
determining file access, changing mode or ownership the vfs will verify
that the caller is privileged over the inode. Extend the various helpers
to handle idmapped mounts. If the inode is accessed through an idmapped
mount map it into the mount's user namespace. Afterwards the permissions
checks are identical to non-idmapped mounts. When changing file
ownership we need to map the uid and gid from the mount's user
namespace. If the initial user namespace is passed nothing changes so
non-idmapped mounts will see identical behavior as before.

Link: https://lore.kernel.org/r/20210112220124.837960-24-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
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

/* v3 */
- David Howells <dhowells@redhat.com>:
  - Remove mnt_idmapped() check after removing mnt_idmapped() helper in earlier
    patches.

/* v4 */
- Serge Hallyn <serge@hallyn.com>:
  - Use "mnt_userns" to refer to a vfsmount's userns everywhere to make
    terminology consistent.

/* v5 */
unchanged
base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837

- Christoph Hellwig <hch@lst.de>:
  - Use new file_mnt_user_ns() helper.

/* v6 */
base-commit: 19c329f6808995b142b3966301f217c831e7cf31

- Christoph Hellwig <hch@lst.de>:
  - Make use of new path_permission() helper.
---
 fs/open.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

Comments

James Morris Jan. 22, 2021, 4:14 a.m. UTC | #1
On Thu, 21 Jan 2021, Christian Brauner wrote:

> For core file operations such as changing directories or chrooting,
> determining file access, changing mode or ownership the vfs will verify
> that the caller is privileged over the inode. Extend the various helpers
> to handle idmapped mounts. If the inode is accessed through an idmapped
> mount map it into the mount's user namespace. Afterwards the permissions
> checks are identical to non-idmapped mounts. When changing file
> ownership we need to map the uid and gid from the mount's user
> namespace. If the initial user namespace is passed nothing changes so
> non-idmapped mounts will see identical behavior as before.
> 
> Link: https://lore.kernel.org/r/20210112220124.837960-24-christian.brauner@ubuntu.com
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: David Howells <dhowells@redhat.com>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Cc: linux-fsdevel@vger.kernel.org
> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>


Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Christoph Hellwig Jan. 22, 2021, 5:21 p.m. UTC | #2
Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>
diff mbox series

Patch

diff --git a/fs/open.c b/fs/open.c
index 8b3f3eb652d0..4ec3979d0466 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -438,7 +438,7 @@  static long do_faccessat(int dfd, const char __user *filename, int mode, int fla
 			goto out_path_release;
 	}
 
-	res = inode_permission(&init_user_ns, inode, mode | MAY_ACCESS);
+	res = inode_permission(mnt_user_ns(path.mnt), inode, mode | MAY_ACCESS);
 	/* SuS v2 requires we report a read only fs too */
 	if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
 		goto out_path_release;
@@ -582,8 +582,8 @@  int chmod_common(const struct path *path, umode_t mode)
 		goto out_unlock;
 	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
-	error = notify_change(&init_user_ns, path->dentry, &newattrs,
-			      &delegated_inode);
+	error = notify_change(mnt_user_ns(path->mnt), path->dentry,
+			      &newattrs, &delegated_inode);
 out_unlock:
 	inode_unlock(inode);
 	if (delegated_inode) {
@@ -644,6 +644,7 @@  SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
 
 int chown_common(const struct path *path, uid_t user, gid_t group)
 {
+	struct user_namespace *mnt_userns;
 	struct inode *inode = path->dentry->d_inode;
 	struct inode *delegated_inode = NULL;
 	int error;
@@ -654,6 +655,10 @@  int chown_common(const struct path *path, uid_t user, gid_t group)
 	uid = make_kuid(current_user_ns(), user);
 	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);
+
 retry_deleg:
 	newattrs.ia_valid =  ATTR_CTIME;
 	if (user != (uid_t) -1) {
@@ -674,7 +679,7 @@  int chown_common(const struct path *path, uid_t user, gid_t group)
 	inode_lock(inode);
 	error = security_path_chown(path, uid, gid);
 	if (!error)
-		error = notify_change(&init_user_ns, path->dentry, &newattrs,
+		error = notify_change(mnt_userns, path->dentry, &newattrs,
 				      &delegated_inode);
 	inode_unlock(inode);
 	if (delegated_inode) {