LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Yafang Shao <laoar.shao@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Petr Mladek <pmladek@suse.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Kees Cook <keescook@chromium.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	qiang.zhang@windriver.com, robdclark@chromium.org,
	Al Viro <viro@zeniv.linux.org.uk>,
	christian@brauner.io, Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/5] kernel/fork: allocate task->comm dynamicly
Date: Wed, 29 Sep 2021 21:08:47 +0800	[thread overview]
Message-ID: <CALOAHbBy60ik+Crf0E8spTyCqth0mPO7+u=ZsQRsbsJS7n6fGA@mail.gmail.com> (raw)
In-Reply-To: <20210929115036.4851-3-laoar.shao@gmail.com>

On Wed, Sep 29, 2021 at 7:51 PM Yafang Shao <laoar.shao@gmail.com> wrote:
>
> task->comm is defined as an array embedded in struct task_struct before.
> This patch changes it to a char pointer. It will be allocated in the fork
> and freed when the task is freed.
>
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> ---
>  include/linux/sched.h |  2 +-
>  kernel/fork.c         | 19 +++++++++++++++++++
>  2 files changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index e12b524426b0..b387b5943db4 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1051,7 +1051,7 @@ struct task_struct {
>          * - access it with [gs]et_task_comm()
>          * - lock it with task_lock()
>          */
> -       char                            comm[TASK_COMM_LEN];
> +       char                            *comm;
>
>         struct nameidata                *nameidata;
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 38681ad44c76..227aec240501 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -721,6 +721,20 @@ static void mmdrop_async(struct mm_struct *mm)
>         }
>  }
>
> +static int task_comm_alloc(struct task_struct *p)
> +{
> +       p->comm = kzalloc(TASK_COMM_LEN, GFP_KERNEL);
> +       if (!p->comm)
> +               return -ENOMEM;
> +
> +       return 0;
> +}
> +
> +static void task_comm_free(struct task_struct *p)
> +{
> +       kfree(p->comm);
> +}
> +
>  static inline void free_signal_struct(struct signal_struct *sig)
>  {
>         taskstats_tgid_free(sig);
> @@ -753,6 +767,7 @@ void __put_task_struct(struct task_struct *tsk)
>         bpf_task_storage_free(tsk);
>         exit_creds(tsk);
>         delayacct_tsk_free(tsk);
> +       task_comm_free(tsk);
>         put_signal_struct(tsk->signal);
>         sched_core_free(tsk);
>
> @@ -2076,6 +2091,10 @@ static __latent_entropy struct task_struct *copy_process(
>         if (data_race(nr_threads >= max_threads))
>                 goto bad_fork_cleanup_count;
>
> +       retval = task_comm_alloc(p);
> +       if (retval)
> +               goto bad_fork_cleanup_count;
> +
>         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
>         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY);
>         p->flags |= PF_FORKNOEXEC;
> --
> 2.17.1
>

After sending the series, I find that I forget to move the
task_comm_alloc() to the end of fork().  Below is the updated one,

---
 include/linux/sched.h |  2 +-
 kernel/fork.c         | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index e12b524426b0..b387b5943db4 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1051,7 +1051,7 @@ struct task_struct {
         * - access it with [gs]et_task_comm()
         * - lock it with task_lock()
         */
-       char                            comm[TASK_COMM_LEN];
+       char                            *comm;

        struct nameidata                *nameidata;

diff --git a/kernel/fork.c b/kernel/fork.c
index 38681ad44c76..d1e0c38464ed 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -721,6 +721,20 @@ static void mmdrop_async(struct mm_struct *mm)
        }
 }

+static int task_comm_alloc(struct task_struct *p)
+{
+       p->comm = kzalloc(TASK_COMM_LEN, GFP_KERNEL);
+       if (!p->comm)
+               return -ENOMEM;
+
+       return 0;
+}
+
+static void task_comm_free(struct task_struct *p)
+{
+       kfree(p->comm);
+}
+
 static inline void free_signal_struct(struct signal_struct *sig)
 {
        taskstats_tgid_free(sig);
@@ -753,6 +767,7 @@ void __put_task_struct(struct task_struct *tsk)
        bpf_task_storage_free(tsk);
        exit_creds(tsk);
        delayacct_tsk_free(tsk);
+       task_comm_free(tsk);
        put_signal_struct(tsk->signal);
        sched_core_free(tsk);

@@ -2352,6 +2367,10 @@ static __latent_entropy struct task_struct *copy_process(
                goto bad_fork_cancel_cgroup;
        }

+       retval = task_comm_alloc(p);
+       if (retval)
+               goto bad_fork_cancel_cgroup;
+
        /* past the last point of failure */
        if (pidfile)
                fd_install(pidfd, pidfile);


-- 
Thanks
Yafang

  reply	other threads:[~2021-09-29 13:09 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-29 11:50 [PATCH 0/5] kthread: increase the size of kthread's comm Yafang Shao
2021-09-29 11:50 ` [PATCH 1/5] kernel: replace sizeof(task->comm) with TASK_COMM_LEN Yafang Shao
2021-09-29 18:09   ` Kees Cook
2021-09-30 12:27     ` Yafang Shao
2021-10-03  3:31   ` Al Viro
2021-10-03 14:14     ` Yafang Shao
2021-09-29 11:50 ` [PATCH 2/5] kernel/fork: allocate task->comm dynamicly Yafang Shao
2021-09-29 13:08   ` Yafang Shao [this message]
2021-09-29 18:11   ` Kees Cook
2021-09-30 12:41     ` Yafang Shao
2021-09-30 14:51       ` Petr Mladek
2021-10-01 11:58         ` Yafang Shao
2021-09-29 11:50 ` [PATCH 3/5] kernel/sched: improve the BUILD_BUG_ON() in get_task_comm() Yafang Shao
2021-09-29 18:12   ` Kees Cook
2021-09-30 12:43     ` Yafang Shao
2021-09-29 11:50 ` [PATCH 4/5] kernel: increase the size of kthread's comm Yafang Shao
2021-09-29 18:19   ` Kees Cook
2021-09-30 12:53     ` Yafang Shao
2021-09-29 11:50 ` [PATCH 5/5] kernel/kthread: show a warning if kthread's comm is still trucated Yafang Shao
2021-09-29 18:20   ` Kees Cook
2021-09-30 12:54     ` Yafang Shao
2021-09-30 15:17   ` Petr Mladek
2021-10-01 11:59     ` Yafang Shao
2021-10-03  3:41 ` [PATCH 0/5] kthread: increase the size of kthread's comm Al Viro
2021-10-03 14:20   ` Yafang Shao

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='CALOAHbBy60ik+Crf0E8spTyCqth0mPO7+u=ZsQRsbsJS7n6fGA@mail.gmail.com' \
    --to=laoar.shao@gmail.com \
    --cc=akpm@linux-foundation.org \
    --cc=christian@brauner.io \
    --cc=dietmar.eggemann@arm.com \
    --cc=keescook@chromium.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mathieu.desnoyers@efficios.com \
    --cc=peterz@infradead.org \
    --cc=pmladek@suse.com \
    --cc=qiang.zhang@windriver.com \
    --cc=robdclark@chromium.org \
    --cc=valentin.schneider@arm.com \
    --cc=viro@zeniv.linux.org.uk \
    --subject='Re: [PATCH 2/5] kernel/fork: allocate task->comm dynamicly' \
    /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

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).