Merge branch 'userns-for-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull user namespace update from Eric Biederman:
"There are several pieces of active development, but only a single
change made it through the gauntlet to be ready for v5.12. That change
is tightening up the semantics of the v3 capabilities xattr. It is
just short of being a bug-fix/security issue as no user space is known
to even generate the problem case"
* 'userns-for-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
capabilities: Don't allow writing ambiguous v3 file capabilities
diff --git a/security/commoncap.c b/security/commoncap.c
index 26c1cb7..78598be 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -500,7 +500,8 @@
__u32 magic, nsmagic;
struct inode *inode = d_backing_inode(dentry);
struct user_namespace *task_ns = current_user_ns(),
- *fs_ns = inode->i_sb->s_user_ns;
+ *fs_ns = inode->i_sb->s_user_ns,
+ *ancestor;
kuid_t rootid;
size_t newsize;
@@ -523,6 +524,15 @@
if (nsrootid == -1)
return -EINVAL;
+ /*
+ * Do not allow allow adding a v3 filesystem capability xattr
+ * if the rootid field is ambiguous.
+ */
+ for (ancestor = task_ns->parent; ancestor; ancestor = ancestor->parent) {
+ if (from_kuid(ancestor, rootid) == 0)
+ return -EINVAL;
+ }
+
newsize = sizeof(struct vfs_ns_cap_data);
nscap = kmalloc(newsize, GFP_ATOMIC);
if (!nscap)
