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authorChristian Brauner <christian.brauner@ubuntu.com>2021-05-11 16:30:15 +0200
committerChristian Brauner <christian.brauner@ubuntu.com>2021-05-12 14:13:16 +0200
commit2ca4dcc4909d787ee153272f7efc2bff3b498720 (patch)
tree730c43aa2706393f338200da6eb1ba333487d244 /fs
parent6efb943b8616ec53a5e444193dccf1af9ad627b5 (diff)
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')
-rw-r--r--fs/namespace.c6
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. */