[PATCH v3 12/21] fs: Refuse uid/gid changes which don't map into s_user_ns

Seth Forshee
2016-04-22T15:39:44Z

Add checks to inode_change_ok to verify that uid and gid changes
will map into the superblock's user namespace. If they do not
fail with -EOVERFLOW. This cannot be overriden with ATTR_FORCE.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
---
fs/attr.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/fs/attr.c b/fs/attr.c
index 25b24d0f6c88..3cfaaac4a18e 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -42,6 +42,17 @@ int inode_change_ok(const struct inode *inode, struct iattr *attr)
return error;
}

+ /*
+ * Verify that uid/gid changes are valid in the target namespace
+ * of the superblock. This cannot be overriden using ATTR_FORCE.
+ */
+ if (ia_valid & ATTR_UID &&
+ from_kuid(inode->i_sb->s_user_ns, attr->ia_uid) == (uid_t)-1)
+ return -EOVERFLOW;
+ if (ia_valid & ATTR_GID &&
+ from_kgid(inode->i_sb->s_user_ns, attr->ia_gid) == (gid_t)-1)
+ return -EOVERFLOW;
+
/* If force is set do it anyway. */
if (ia_valid & ATTR_FORCE)
return 0;
--
1.9.1