From: Oleg Nesterov <oleg@redhat.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Kees Cook <keescook@chromium.org>,
Roland McGrath <roland@hack.frob.com>,
Al Viro <viro@ZenIV.linux.org.uk>,
David Howells <dhowells@redhat.com>,
"Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Subject: Re: [PATCH 06/26] rlimit: Remove unnecessary grab of tasklist_lock
Date: Wed, 7 Jun 2017 14:36:57 +0200 [thread overview]
Message-ID: <20170607123657.GA22199@redhat.com> (raw)
In-Reply-To: <20170606190338.28347-6-ebiederm@xmission.com>
Hi Eric,
I'll try very much to read this series tomorrow, can't do this today...
On 06/06, Eric W. Biederman wrote:
>
> @@ -1380,13 +1380,6 @@ int do_prlimit(struct task_struct *tsk, unsigned int resource,
> return -EPERM;
> }
>
> - /* protect tsk->signal and tsk->sighand from disappearing */
> - read_lock(&tasklist_lock);
> - if (!tsk->sighand) {
> - retval = -ESRCH;
> - goto out;
> - }
Yes, the comment is wrong.
However we do need read_lock(tasklist_lock) to access ->group_leader. And the
->sighand != NULL check ensures that ->group_leader is the valid pointer.
Also, update_rlimit_cpu() is not safe without tasklist / sighand-check.
We can probably change this code to rely on rcu.
Oleg.
next prev parent reply other threads:[~2017-06-07 12:37 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-06 19:01 [PATCH 00/26] Fixing wait, exit, ptrace, exec, and CLONE_THREAD Eric W. Biederman
2017-06-06 19:03 ` [PATCH 01/26] alpha: Remove unused TASK_GROUP_LEADER Eric W. Biederman
2017-06-06 19:03 ` [PATCH 02/26] cgroup: Don't open code tasklist_empty() Eric W. Biederman
2017-06-06 19:03 ` [PATCH 03/26] signal: Do not perform permission checks when sending pdeath_signal Eric W. Biederman
2017-06-06 20:01 ` Linus Torvalds
2017-06-07 11:23 ` Eric W. Biederman
2017-06-06 21:42 ` Richard Weinberger
2017-06-06 19:03 ` [PATCH 04/26] signal: Make group_send_sig_info static Eric W. Biederman
2017-06-06 19:03 ` [PATCH 05/26] exit: Remove the pointless clearing of SIGPENDING in __exit_signal Eric W. Biederman
2017-06-06 19:03 ` [PATCH 06/26] rlimit: Remove unnecessary grab of tasklist_lock Eric W. Biederman
2017-06-07 12:36 ` Oleg Nesterov [this message]
2017-06-07 14:08 ` Eric W. Biederman
2017-06-06 19:03 ` [PATCH 07/26] pidns: Improve the error handling in alloc_pid Eric W. Biederman
2017-06-06 19:03 ` [PATCH 08/26] exit: Make the runqueue rcu safe Eric W. Biederman
2017-06-07 13:16 ` Oleg Nesterov
2017-06-06 19:03 ` [PATCH 09/26] signal: Don't allow sending SIGKILL or SIGSTOP to init Eric W. Biederman
2017-06-06 19:03 ` [PATCH 10/26] ptrace: Simplify ptrace_detach & exit_ptrace Eric W. Biederman
2017-06-06 19:03 ` [PATCH 11/26] wait: Properly implement __WCLONE handling in the presence of exec and ptrace Eric W. Biederman
2017-06-06 19:03 ` [PATCH 12/26] wait: Directly test for the two cases where wait_task_zombie is called Eric W. Biederman
2017-06-06 19:03 ` [PATCH 13/26] wait: Remove unused delay_group_leader Eric W. Biederman
2017-06-06 19:03 ` [PATCH 14/26] wait: Move changing of ptrace from wait_consider_task into wait_task_stopped Eric W. Biederman
2017-06-06 19:03 ` [PATCH 15/26] wait: Don't delay !ptrace_reparented leaders Eric W. Biederman
2017-06-06 19:03 ` [PATCH 16/26] exit: Fix reporting a ptraced !reparented leader has exited Eric W. Biederman
2017-06-06 19:03 ` [PATCH 17/26] exit: Rework the exit states for ptracees Eric W. Biederman
2017-06-06 19:03 ` [PATCH 18/26] wait: Fix WSTOPPED on a ptraced child Eric W. Biederman
2017-06-06 19:03 ` [PATCH 19/26] wait: Simpler code for clearing notask_error in wait_consider_task Eric W. Biederman
2017-06-06 19:03 ` [PATCH 20/26] wait: Don't pass the list to wait_consider_task Eric W. Biederman
2017-06-06 19:03 ` [PATCH 21/26] wait: Optmize waitpid Eric W. Biederman
2017-06-06 19:03 ` [PATCH 22/26] exit: Fix auto-wait of ptraced children Eric W. Biederman
2017-06-06 19:03 ` [PATCH 23/26] signal: Fix SIGCONT before group stop completes Eric W. Biederman
2017-06-06 19:03 ` [PATCH 24/26] signal: In ptrace_stop improve identical signal detection Eric W. Biederman
2017-06-06 19:03 ` [PATCH 25/26] signal: In ptrace_stop use CLD_TRAPPED in all ptrace signals Eric W. Biederman
2017-06-06 19:03 ` [PATCH 26/26] pidns: Ensure zap_pid_ns_processes always terminates Eric W. Biederman
2017-06-06 19:40 ` [PATCH 00/26] Fixing wait, exit, ptrace, exec, and CLONE_THREAD Aleksa Sarai
2017-06-07 11:36 ` Eric W. Biederman
2017-06-07 12:21 ` Aleksa Sarai
2017-06-06 20:07 ` Linus Torvalds
2017-06-07 15:59 ` Eric W. Biederman
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