On Wed, Sep 29, 2021 at 7:51 PM Yafang Shao <[email protected]> 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 <[email protected]>
> ---
> 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