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| author | Christian Brauner <christian.brauner@ubuntu.com> | 2021-05-11 16:30:15 +0200 |
|---|---|---|
| committer | Christian Brauner <christian.brauner@ubuntu.com> | 2021-05-12 14:13:16 +0200 |
| commit | 2ca4dcc4909d787ee153272f7efc2bff3b498720 (patch) | |
| tree | 730c43aa2706393f338200da6eb1ba333487d244 /fs/namespace.c | |
| parent | Linux 5.13-rc1 (diff) | |
| download | linux-2ca4dcc4909d787ee153272f7efc2bff3b498720.tar.xz linux-2ca4dcc4909d787ee153272f7efc2bff3b498720.zip | |
fs/mount_setattr: tighten permission checks
We currently don't have any filesystems that support idmapped mounts
which are mountable inside a user namespace. That was a deliberate
decision for now as a userns root can just mount the filesystem
themselves. So enforce this restriction explicitly until there's a real
use-case for this. This way we can notice it and will have a chance to
adapt and audit our translation helpers and fstests appropriately if we
need to support such filesystems.
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org
CC: linux-fsdevel@vger.kernel.org
Suggested-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index f63337828e1c..c3f1a78ba369 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3855,8 +3855,12 @@ static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) if (!(m->mnt_sb->s_type->fs_flags & FS_ALLOW_IDMAP)) return -EINVAL; + /* Don't yet support filesystem mountable in user namespaces. */ + if (m->mnt_sb->s_user_ns != &init_user_ns) + return -EINVAL; + /* We're not controlling the superblock. */ - if (!ns_capable(m->mnt_sb->s_user_ns, CAP_SYS_ADMIN)) + if (!capable(CAP_SYS_ADMIN)) return -EPERM; /* Mount has already been visible in the filesystem hierarchy. */ |