[review,01/11] fs: Refuse uid/gid changes which don't map into s_user_ns

Commit Message

Eric W. Biederman July 2, 2016, 5:20 p.m. UTC

From: Seth Forshee <[e-mail]>

Add checks to notify_change to verify that uid and gid changes
will map into the superblock's user namespace. If they do not
fail with -EOVERFLOW.

This is mandatory so that fileystems don't have to even think
of dealing with ia_uid and ia_gid that

--EWB Moved the test from inode_change_ok to notify_change

Signed-off-by: Seth Forshee <[e-mail]>
Acked-by: Serge Hallyn <[e-mail]>
Signed-off-by: Eric W. Biederman <[e-mail]>
---
 fs/attr.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

Patch

diff --git a/fs/attr.c b/fs/attr.c
index 25b24d0f6c88..dd723578ddce 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -255,6 +255,17 @@  int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **de
 	if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
 		return 0;
 
+	/*
+	 * Verify that uid/gid changes are valid in the target
+	 * namespace of the superblock.
+	 */
+	if (ia_valid & ATTR_UID &&
+	    !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid))
+		return -EOVERFLOW;
+	if (ia_valid & ATTR_GID &&
+	    !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid))
+		return -EOVERFLOW;
+
 	error = security_inode_setattr(dentry, attr);
 	if (error)
 		return error;