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@xxxxxxxxxx Cc: Christoph Hellwig <hch@xxxxxx> Cc: David Howells <dhowells@xxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: linux-fsdevel@xxxxxxxxxxxxxxx Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx> --- /* v2 */ unchanged /* v3 */ - David Howells <dhowells@xxxxxxxxxx>: - Remove mnt_idmapped() check after removing mnt_idmapped() helper in earlier patches. /* v4 */ - Serge Hallyn <serge@xxxxxxxxxx>: - Use "mnt_userns" to refer to a vfsmount's userns everywhere to make terminology consistent. /* v5 */ unchanged base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837 - Christoph Hellwig <hch@xxxxxx>: - Use new file_mnt_user_ns() helper. /* v6 */ base-commit: 19c329f6808995b142b3966301f217c831e7cf31 - Christoph Hellwig <hch@xxxxxx>: - Make use of new path_permission() helper. --- fs/open.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) 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) { -- 2.30.0
