Add a reference to ucounts for each cred
For RLIMIT_NPROC and some other rlimits the user_struct that holds the
global limit is kept alive for the lifetime of a process by keeping it
in struct cred. Adding a pointer to ucounts in the struct cred will
allow to track RLIMIT_NPROC not only for user in the system, but for
user in the user_namespace.
Updating ucounts may require memory allocation which may fail. So, we
cannot change cred.ucounts in the commit_creds() because this function
cannot fail and it should always return 0. For this reason, we modify
cred.ucounts before calling the commit_creds().
Changelog
v6:
* Fix null-ptr-deref in is_ucounts_overlimit() detected by trinity. This
error was caused by the fact that cred_alloc_blank() left the ucounts
pointer empty.
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://lkml.kernel.org/r/b37aaef28d8b9b0d757e07ba6dd27281bbe39259.1619094428.git.legion@kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 9a4b980..f1b7b4b 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -1340,6 +1340,9 @@ static int userns_install(struct nsset *nsset, struct ns_common *ns)
put_user_ns(cred->user_ns);
set_cred_user_ns(cred, get_user_ns(user_ns));
+ if (set_cred_ucounts(cred) < 0)
+ return -EINVAL;
+
return 0;
}