linux-kernel - Re: [PATCH 07/22] pidfs: drop struct pidfs_exit

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Message-ID: <CAJqdLrpCH9wsJUo0F2a9XVTFWav-jE--m+KoV5KF0Dqp2qU9hg@mail.gmail.com>
Date: Tue, 4 Nov 2025 09:45:32 +0100
From: Alexander Mikhalitsyn <alexander@...alicyn.com>
To: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>, 
	Amir Goldstein <amir73il@...il.com>, Aleksa Sarai <cyphar@...har.com>, 
	Yu Watanabe <watanabe.yu+github@...il.com>, Josef Bacik <josef@...icpanda.com>, 
	Jeff Layton <jlayton@...nel.org>, Jann Horn <jannh@...gle.com>, 
	Luca Boccassi <luca.boccassi@...il.com>, linux-kernel@...r.kernel.org, 
	Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>, 
	Lennart Poettering <lennart@...ttering.net>, Mike Yuan <me@...dnzj.com>, 
	Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>
Subject: Re: [PATCH 07/22] pidfs: drop struct pidfs_exit_info

Am Di., 28. Okt. 2025 um 09:46 Uhr schrieb Christian Brauner
<brauner@...nel.org>:
>
> This is not needed anymore now that we have the new scheme to guarantee
> all-or-nothing information exposure.
>
> Signed-off-by: Christian Brauner <brauner@...nel.org>

Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>

> ---
>  fs/pidfs.c | 35 +++++++++++------------------------
>  1 file changed, 11 insertions(+), 24 deletions(-)
>
> diff --git a/fs/pidfs.c b/fs/pidfs.c
> index 0fad0c969b7a..a3b80be3b98b 100644
> --- a/fs/pidfs.c
> +++ b/fs/pidfs.c
> @@ -39,16 +39,6 @@ void pidfs_get_root(struct path *path)
>         path_get(path);
>  }
>
> -/*
> - * Stashes information that userspace needs to access even after the
> - * process has been reaped.
> - */
> -struct pidfs_exit_info {
> -       __u64 cgroupid;
> -       __s32 exit_code;
> -       __u32 coredump_mask;
> -};
> -
>  enum pidfs_attr_mask_bits {
>         PIDFS_ATTR_BIT_EXIT     = 0,
>  };
> @@ -56,8 +46,11 @@ enum pidfs_attr_mask_bits {
>  struct pidfs_attr {
>         unsigned long attr_mask;
>         struct simple_xattrs *xattrs;
> -       struct pidfs_exit_info __pei;
> -       struct pidfs_exit_info *exit_info;
> +       struct /* exit info */ {
> +               __u64 cgroupid;
> +               __s32 exit_code;
> +       };
> +       __u32 coredump_mask;
>  };
>
>  static struct rb_root pidfs_ino_tree = RB_ROOT;
> @@ -313,7 +306,6 @@ static long pidfd_info(struct file *file, unsigned int cmd, unsigned long arg)
>         struct pid *pid = pidfd_pid(file);
>         size_t usize = _IOC_SIZE(cmd);
>         struct pidfd_info kinfo = {};
> -       struct pidfs_exit_info *exit_info;
>         struct user_namespace *user_ns;
>         struct pidfs_attr *attr;
>         const struct cred *c;
> @@ -342,15 +334,15 @@ static long pidfd_info(struct file *file, unsigned int cmd, unsigned long arg)
>                         smp_rmb();
>                         kinfo.mask |= PIDFD_INFO_EXIT;
>  #ifdef CONFIG_CGROUPS
> -                       kinfo.cgroupid = exit_info->cgroupid;
> +                       kinfo.cgroupid = attr->cgroupid;
>                         kinfo.mask |= PIDFD_INFO_CGROUPID;
>  #endif
> -                       kinfo.exit_code = exit_info->exit_code;
> +                       kinfo.exit_code = attr->exit_code;
>                 }
>         }
>
>         if (mask & PIDFD_INFO_COREDUMP) {
> -               kinfo.coredump_mask = READ_ONCE(attr->__pei.coredump_mask);
> +               kinfo.coredump_mask = READ_ONCE(attr->coredump_mask);
>                 if (kinfo.coredump_mask)
>                         kinfo.mask |= PIDFD_INFO_COREDUMP;
>         }
> @@ -629,7 +621,6 @@ void pidfs_exit(struct task_struct *tsk)
>  {
>         struct pid *pid = task_pid(tsk);
>         struct pidfs_attr *attr;
> -       struct pidfs_exit_info *exit_info;
>  #ifdef CONFIG_CGROUPS
>         struct cgroup *cgrp;
>  #endif
> @@ -657,15 +648,13 @@ void pidfs_exit(struct task_struct *tsk)
>          * is put
>          */
>
> -       exit_info = &attr->__pei;
> -
>  #ifdef CONFIG_CGROUPS
>         rcu_read_lock();
>         cgrp = task_dfl_cgroup(tsk);
> -       exit_info->cgroupid = cgroup_id(cgrp);
> +       attr->cgroupid = cgroup_id(cgrp);
>         rcu_read_unlock();
>  #endif
> -       exit_info->exit_code = tsk->exit_code;
> +       attr->exit_code = tsk->exit_code;
>
>         /* Ensure that PIDFD_GET_INFO sees either all or nothing. */
>         smp_wmb();
> @@ -676,7 +665,6 @@ void pidfs_exit(struct task_struct *tsk)
>  void pidfs_coredump(const struct coredump_params *cprm)
>  {
>         struct pid *pid = cprm->pid;
> -       struct pidfs_exit_info *exit_info;
>         struct pidfs_attr *attr;
>         __u32 coredump_mask = 0;
>
> @@ -685,14 +673,13 @@ void pidfs_coredump(const struct coredump_params *cprm)
>         VFS_WARN_ON_ONCE(!attr);
>         VFS_WARN_ON_ONCE(attr == PIDFS_PID_DEAD);
>
> -       exit_info = &attr->__pei;
>         /* Note how we were coredumped. */
>         coredump_mask = pidfs_coredump_mask(cprm->mm_flags);
>         /* Note that we actually did coredump. */
>         coredump_mask |= PIDFD_COREDUMPED;
>         /* If coredumping is set to skip we should never end up here. */
>         VFS_WARN_ON_ONCE(coredump_mask & PIDFD_COREDUMP_SKIP);
> -       smp_store_release(&exit_info->coredump_mask, coredump_mask);
> +       smp_store_release(&attr->coredump_mask, coredump_mask);
>  }
>  #endif
>
>
> --
> 2.47.3
>