linux-kernel - Re: [PATCH v2] Fix regression due to "fs: move binfmt

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Message-ID: <YgklDvNecca1/8in@shredder>
Date:   Sun, 13 Feb 2022 17:34:38 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Domenico Andreoli <domenico.andreoli@...ux.com>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Tong Zhang <ztong0001@...il.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        David Airlie <airlied@...ux.ie>,
        Andrew Morton <akpm@...ux-foundation.org>, amir73il@...il.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Arnd Bergmann <arnd@...db.de>, bcrl@...ck.org,
        benh@...nel.crashing.org, clemens@...isch.de, crope@....fi,
        dgilbert@...erlog.com, Greg KH <gregkh@...uxfoundation.org>,
        jack@...e.cz, jani.nikula@...el.com, jani.nikula@...ux.intel.com,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>, jlbec@...lplan.org,
        john.ogness@...utronix.de, joonas.lahtinen@...ux.intel.com,
        Joseph Qi <joseph.qi@...ux.alibaba.com>, julia.lawall@...ia.fr,
        Kees Cook <keescook@...omium.org>, kernel@...force.de,
        Linux Memory Management List <linux-mm@...ck.org>,
        mark@...heh.com, "Martin K. Petersen" <martin.petersen@...cle.com>,
        mm-commits@...r.kernel.org, nixiaoming@...wei.com,
        penguin-kernel@...ove.sakura.ne.jp, peterz@...radead.org,
        phil@...lpotter.co.uk, pjt@...gle.com, pmladek@...e.com,
        rafael@...nel.org, rodrigo.vivi@...el.com, rostedt@...dmis.org,
        senozhatsky@...omium.org, sre@...nel.org, steve@....org,
        surenb@...gle.com, torvalds@...ux-foundation.org, tytso@....edu,
        Al Viro <viro@...iv.linux.org.uk>, wangqing@...o.com,
        Iurii Zaikin <yzaikin@...gle.com>,
        open list <linux-kernel@...r.kernel.org>,
        regressions@...ts.linux.dev
Subject: Re: [PATCH v2] Fix regression due to "fs: move binfmt_misc sysctl to
 its own file"

On Wed, Feb 09, 2022 at 08:49:20AM +0100, Domenico Andreoli wrote:
>  fs/binfmt_misc.c |    6 +-----
>  fs/file_table.c  |    2 ++
>  2 files changed, 3 insertions(+), 5 deletions(-)
> 
> Index: b/fs/binfmt_misc.c
> ===================================================================
> --- a/fs/binfmt_misc.c
> +++ b/fs/binfmt_misc.c
> @@ -817,20 +817,16 @@ static struct file_system_type bm_fs_typ
>  };
>  MODULE_ALIAS_FS("binfmt_misc");
>  
> -static struct ctl_table_header *binfmt_misc_header;
> -
>  static int __init init_misc_binfmt(void)
>  {
>  	int err = register_filesystem(&bm_fs_type);
>  	if (!err)
>  		insert_binfmt(&misc_format);
> -	binfmt_misc_header = register_sysctl_mount_point("fs/binfmt_misc");
> -	return 0;
> +	return err;
>  }
>  
>  static void __exit exit_misc_binfmt(void)
>  {
> -	unregister_sysctl_table(binfmt_misc_header);
>  	unregister_binfmt(&misc_format);
>  	unregister_filesystem(&bm_fs_type);
>  }
> Index: b/fs/file_table.c
> ===================================================================
> --- a/fs/file_table.c
> +++ b/fs/file_table.c
> @@ -119,6 +119,8 @@ static struct ctl_table fs_stat_sysctls[
>  static int __init init_fs_stat_sysctls(void)
>  {
>  	register_sysctl_init("fs", fs_stat_sysctls);
> +	if (IS_ENABLED(CONFIG_BINFMT_MISC))
> +		register_sysctl_mount_point("fs/binfmt_misc");

Hi,

kmemleak complains about this:

# cat /sys/kernel/debug/kmemleak
unreferenced object 0xffff8881045fea88 (size 96):
  comm "swapper/0", pid 1, jiffies 4294669355 (age 167.804s)
  hex dump (first 32 bytes):
    e0 c8 07 88 ff ff ff ff 00 00 00 00 01 00 00 00  ................
    01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff81d11637>] __register_sysctl_table+0x117/0x1150
    [<ffffffff86c3600f>] init_fs_stat_sysctls+0x30/0x33
    [<ffffffff81002558>] do_one_initcall+0x108/0x690
    [<ffffffff86bca8bd>] kernel_init_freeable+0x45a/0x4de
    [<ffffffff83e0757f>] kernel_init+0x1f/0x220
    [<ffffffff810048cf>] ret_from_fork+0x1f/0x30

>  	return 0;
>  }
>  fs_initcall(init_fs_stat_sysctls);
>