From: Oleg Nesterov <oleg@redhat.com>
To: Adrian Reber <areber@redhat.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>,
Eric Biederman <ebiederm@xmission.com>,
Pavel Emelyanov <ovzxemul@gmail.com>,
Jann Horn <jannh@google.com>,
Dmitry Safonov <0x7f454c46@gmail.com>,
linux-kernel@vger.kernel.org, Andrei Vagin <avagin@gmail.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Radostin Stoyanov <rstoyanov1@gmail.com>
Subject: Re: [PATCH v7 1/2] fork: extend clone3() to support setting a PID
Date: Mon, 11 Nov 2019 16:25:15 +0100 [thread overview]
Message-ID: <20191111152514.GA11389@redhat.com> (raw)
In-Reply-To: <20191111131704.656169-1-areber@redhat.com>
On 11/11, Adrian Reber wrote:
>
> v7:
> - changed set_tid to be an array to set the PID of a process
> in multiple nested PID namespaces at the same time as discussed
> at LPC 2019 (container MC)
cough... iirc you convinced me this is not needed when we discussed
the previous version ;) Nevermind, probably my memory fools me.
So far I only have some cosmetic nits,
> @@ -175,6 +187,18 @@ struct pid *alloc_pid(struct pid_namespace *ns)
>
> for (i = ns->level; i >= 0; i--) {
> int pid_min = 1;
> + int t_pos = 0;
^^^^^
I won't insist, but I'd suggest to cache set_tid[t_pos] instead to make
the code a bit more simple.
> @@ -186,12 +210,24 @@ struct pid *alloc_pid(struct pid_namespace *ns)
> if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS)
> pid_min = RESERVED_PIDS;
You can probably move this code into the "else" branch below.
IOW, something like
for (i = ns->level; i >= 0; i--) {
int xxx = 0;
if (set_tid_size) {
int pos = ns->level - i;
xxx = set_tid[pos];
if (xxx < 1 || xxx >= pid_max)
return ERR_PTR(-EINVAL);
/* Also fail if a PID != 1 is requested and no PID 1 exists */
if (xxx != 1 && !tmp->child_reaper)
return ERR_PTR(-EINVAL);
if (!ns_capable(tmp->user_ns, CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);
set_tid_size--;
}
idr_preload(GFP_KERNEL);
spin_lock_irq(&pidmap_lock);
if (xxx) {
nr = idr_alloc(&tmp->idr, NULL, xxx, xxx + 1,
GFP_ATOMIC);
/*
* If ENOSPC is returned it means that the PID is
* alreay in use. Return EEXIST in that case.
*/
if (nr == -ENOSPC)
nr = -EEXIST;
} else {
int pid_min = 1;
/*
* init really needs pid 1, but after reaching the
* maximum wrap back to RESERVED_PIDS
*/
if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS)
pid_min = RESERVED_PIDS;
/*
* Store a null pointer so find_pid_ns does not find
* a partially initialized PID (see below).
*/
nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
pid_max, GFP_ATOMIC);
}
...
This way only the "if (set_tid_size)" block has to play with set_tid_size/set_tid.
note also that this way we can easily allow set_tid[some_level] == 0, we can
simply do
- if (xxx < 1 || xxx >= pid_max)
+ if (xxx < 0 || xxx >= pid_max)
although I don't think this is really useful.
Oleg.
next prev parent reply other threads:[~2019-11-11 15:25 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-11 13:17 [PATCH v7 1/2] fork: extend clone3() to support setting a PID Adrian Reber
2019-11-11 13:17 ` [PATCH v7 2/2] selftests: add tests for clone3() Adrian Reber
2019-11-11 15:25 ` Oleg Nesterov [this message]
2019-11-11 15:40 ` [PATCH v7 1/2] fork: extend clone3() to support setting a PID Adrian Reber
2019-11-11 16:14 ` Christian Brauner
2019-11-11 16:32 ` Oleg Nesterov
2019-11-11 23:08 ` Eric W. Biederman
2019-11-12 10:24 ` Christian Brauner
2019-11-11 16:12 ` Christian Brauner
2019-11-11 20:41 ` Rasmus Villemoes
2019-11-12 15:26 ` Adrian Reber
2019-11-13 8:02 ` Adrian Reber
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191111152514.GA11389@redhat.com \
--to=oleg@redhat.com \
--cc=0x7f454c46@gmail.com \
--cc=areber@redhat.com \
--cc=avagin@gmail.com \
--cc=christian.brauner@ubuntu.com \
--cc=ebiederm@xmission.com \
--cc=jannh@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=ovzxemul@gmail.com \
--cc=rppt@linux.ibm.com \
--cc=rstoyanov1@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).