linux-kernel - Re: [PATCH 02/22] pidfs: fix PIDFD_INFO

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Message-ID: <CAJqdLroQrPkjsDfORf6FimbG2-noX43Kw+Z2M7d3DovpFFyjXw@mail.gmail.com>
Date: Mon, 3 Nov 2025 16:35:50 +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 02/22] pidfs: fix PIDFD_INFO_COREDUMP handling

Am Di., 28. Okt. 2025 um 09:46 Uhr schrieb Christian Brauner
<brauner@...nel.org>:
>
> When PIDFD_INFO_COREDUMP is requested we raise it unconditionally in the
> returned mask even if no coredump actually did take place. This was
> done because we assumed that the later check whether ->coredump_mask as
> non-zero detects that it is zero and then retrieves the dumpability
> settings from the task's mm. This has issues though becuase there are
> tasks that might not have any mm. Also it's just not very cleanly
> implemented. Fix this.
>
> Signed-off-by: Christian Brauner <brauner@...nel.org>

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

> ---
>  fs/pidfs.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/fs/pidfs.c b/fs/pidfs.c
> index c2f0b7091cd7..c0f410903c3f 100644
> --- a/fs/pidfs.c
> +++ b/fs/pidfs.c
> @@ -335,8 +335,9 @@ static long pidfd_info(struct file *file, unsigned int cmd, unsigned long arg)
>         }
>
>         if (mask & PIDFD_INFO_COREDUMP) {
> -               kinfo.mask |= PIDFD_INFO_COREDUMP;
>                 kinfo.coredump_mask = READ_ONCE(attr->__pei.coredump_mask);
> +               if (kinfo.coredump_mask)
> +                       kinfo.mask |= PIDFD_INFO_COREDUMP;
>         }
>
>         task = get_pid_task(pid, PIDTYPE_PID);
> @@ -355,12 +356,13 @@ static long pidfd_info(struct file *file, unsigned int cmd, unsigned long arg)
>         if (!c)
>                 return -ESRCH;
>
> -       if ((kinfo.mask & PIDFD_INFO_COREDUMP) && !(kinfo.coredump_mask)) {
> +       if ((mask & PIDFD_INFO_COREDUMP) && !kinfo.coredump_mask) {
>                 guard(task_lock)(task);
>                 if (task->mm) {
>                         unsigned long flags = __mm_flags_get_dumpable(task->mm);
>
>                         kinfo.coredump_mask = pidfs_coredump_mask(flags);
> +                       kinfo.mask |= PIDFD_INFO_COREDUMP;
>                 }
>         }
>
>
> --
> 2.47.3
>