[GIT PULL] ucount fixes for v5.15

[GIT PULL] ucount fixes for v5.15

[Eric W. Biederman]

Linus,

Please pull the ucount-fixes-for-v5.15 branch from the git tree:

  git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git ucount-fixes-for-v5.15

  HEAD: 5ebcbe342b1c12fae44b4f83cbeae1520e09857e ucounts: Move get_ucounts from cred_alloc_blank to key_change_session_keyring

There has been one very hard to track down bug in the ucount code that
we have been tracking since roughly v5.14 was released.  Alex managed to
find a reliable reproducer a few days ago and then I was able to
instrument the code and figure out what the issue was.

It turns out the sigqueue_alloc single atomic operation optimization did
not play nicely with ucounts multiple level rlimits.  It turned out that
either sigqueue_alloc or sigqueue_free could be operating on multiple
levels and trigger the conditions for the optimization on more than one
level at the same time.

To deal with that situation I have introduced inc_rlimit_get_ucounts
and dec_rlimit_put_ucounts that just focuses on the optimization and
the rlimit and ucount changes.

While looking into the big bug I found I couple of other little issues
so I am including those fixes here as well.


When I have time I would very much like to dig into process ownership of
the shared signal queue and see if we could pick a single owner for the
entire queue so that all of the rlimits can count to that owner.  Which
should entirely remove the need to call get_ucounts and put_ucounts
in sigqueue_alloc and sigqueue_free.  It is difficult because Linux
unlike POSIX supports setuid that works on a single thread.

Eric W. Biederman (4):
      ucounts: Fix signal ucount refcounting
      ucounts: Pair inc_rlimit_ucounts with dec_rlimit_ucoutns in commit_creds
      ucounts: Proper error handling in set_cred_ucounts
      ucounts: Move get_ucounts from cred_alloc_blank to key_change_session_keyring

 kernel/cred.c                | 9 ++++-----
 security/keys/process_keys.c | 8 ++++++++
 2 files changed, 12 insertions(+), 5 deletions(-)

Eric

Re: [GIT PULL] ucount fixes for v5.15

[Linus Torvalds]

On Thu, Oct 21, 2021 at 6:04 AM Eric W. Biederman <ebiederm@xmission.com> wrote:
>
>  kernel/cred.c                | 9 ++++-----
>  security/keys/process_keys.c | 8 ++++++++
>  2 files changed, 12 insertions(+), 5 deletions(-)

That's not remotely the right diffstat.

What's going on?

The shortlog was correct, and I pulled the branch, because everything
else looked ok, but that diffstat in the pull request was some
complete fantasy.

If I were to guess, I think the diffstat may be everything _but_ that
first ("ucounts: Fix signal ucount refcounting") fix. I just don't see
how/why you'd get that as part of the pull request.

                  Linus

                     Linus

Re: [GIT PULL] ucount fixes for v5.15

[Eric W. Biederman]

Linus Torvalds <torvalds@linux-foundation.org> writes:

> On Thu, Oct 21, 2021 at 6:04 AM Eric W. Biederman <ebiederm@xmission.com> wrote:
>>
>>  kernel/cred.c                | 9 ++++-----
>>  security/keys/process_keys.c | 8 ++++++++
>>  2 files changed, 12 insertions(+), 5 deletions(-)
>
> That's not remotely the right diffstat.
>
> What's going on?

Sigh.  I sent the diffstat from when I sent the additional patches
out for review instead of the diffstat for the entire branch I was
asking you to pull.

I really should have named things differently on my end when I sent
the additional changes out for review.

The correct diffstat should have been.

 include/linux/user_namespace.h |  2 ++
 kernel/cred.c                  |  9 ++++----
 kernel/signal.c                | 25 ++++++---------------
 kernel/ucount.c                | 49 ++++++++++++++++++++++++++++++++++++++++++
 security/keys/process_keys.c   |  8 +++++++
 5 files changed, 69 insertions(+), 24 deletions(-)


> The shortlog was correct, and I pulled the branch, because everything
> else looked ok, but that diffstat in the pull request was some
> complete fantasy.
>
> If I were to guess, I think the diffstat may be everything _but_ that
> first ("ucounts: Fix signal ucount refcounting") fix. I just don't see
> how/why you'd get that as part of the pull request.

You are exactly right.

My apologies for the confusion.
Eric

Re: [GIT PULL] ucount fixes for v5.15

[pr-tracker-bot]

The pull request you sent on Thu, 21 Oct 2021 11:02:14 -0500:

> git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git ucount-fixes-for-v5.15

has been merged into torvalds/linux.git:
https://git.kernel.org/torvalds/c/9d235ac01f54e8f8c1d967b25ac29e4313a41c5c

Thank you!

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