linux-kernel - [PATCH v2 0/5] ucounts: RLIMIT

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Message-ID: <87ilteiz4a.fsf_-_@email.froward.int.ebiederm.org>
Date:   Wed, 16 Feb 2022 09:56:37 -0600
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     <linux-kernel@...r.kernel.org>
Cc:     Alexey Gladkov <legion@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Shuah Khan <shuah@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        Solar Designer <solar@...nwall.com>,
        Ran Xiaokai <ran.xiaokai@....com.cn>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        Michal Koutný <mkoutny@...e.com>,
        <linux-api@...r.kernel.org>
Subject: [PATCH v2 0/5] ucounts: RLIMIT_NPROC fixes

Michal Koutný recently found some bugs in the enforcement of
RLIMIT_NPROC in the recent ucount rlimit implementation.

I saw some additional bugs and some cleaner ways to fix the problem so
instead of starting with his fixes these are my own.

I have rewritten about half my fixes since the last time this was
posted.  There is this notion (not entirely wrong) that the code should
be consistent and make sense.  When I dug in I discovered that has not
been the case for the last 20 years.  Fixing the long standing
inconsistencies is something that seems to warrent wider vetting on
linux-api.

So with this set of patches I have developed a very conservative
approach changing only what is necessary to fix the bugs that I can
see clearly.  Cleanups and anything that is making the code more
consistent can follow after we have the code working as it has
historically.

Anyone who can please take a look and tell me if I am doing something silly.

Eric W. Biederman (5):
      rlimit: Fix RLIMIT_NPROC enforcement failure caused by capability calls in set_user
      ucounts: Enforce RLIMIT_NPROC not RLIMIT_NPROC+1
      ucounts: Base set_cred_ucounts changes on the real user
      ucounts: Move RLIMIT_NPROC handling after set_user
      ucounts: Handle wrapping in is_ucounts_overlimit

 kernel/cred.c   |  9 ++-------
 kernel/fork.c   | 10 +++++-----
 kernel/sys.c    | 20 ++++++++++++++------
 kernel/ucount.c |  3 ++-
 4 files changed, 23 insertions(+), 19 deletions(-)

Eric