Messages in this thread Patch in this message | | | From | Yafang Shao <> | Date | Wed, 29 Sep 2021 21:08:47 +0800 | Subject | Re: [PATCH 2/5] kernel/fork: allocate task->comm dynamicly |
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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
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