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From: Domenico Andreoli <domenico.andreoli@linux.com>
To: airlied@linux.ie, akpm@linux-foundation.org, amir73il@gmail.com,
	andriy.shevchenko@linux.intel.com, arnd@arndb.de, bcrl@kvack.org,
	benh@kernel.crashing.org, clemens@ladisch.de, crope@iki.fi,
	dgilbert@interlog.com, ebiederm@xmission.com,
	gregkh@linuxfoundation.org, jack@suse.cz, jani.nikula@intel.com,
	jani.nikula@linux.intel.com, jejb@linux.ibm.com,
	jlbec@evilplan.org, john.ogness@linutronix.de,
	joonas.lahtinen@linux.intel.com, joseph.qi@linux.alibaba.com,
	julia.lawall@inria.fr, keescook@chromium.org, kernel@tuxforce.de,
	linux-mm@kvack.org, mark@fasheh.com, martin.petersen@oracle.com,
	mcgrof@kernel.org, mm-commits@vger.kernel.org,
	nixiaoming@huawei.com, penguin-kernel@i-love.sakura.ne.jp,
	peterz@infradead.org, phil@philpotter.co.uk, pjt@google.com,
	pmladek@suse.com, rafael@kernel.org, rodrigo.vivi@intel.com,
	rostedt@goodmis.org, senozhatsky@chromium.org, sre@kernel.org,
	steve@sk2.org, surenb@google.com, torvalds@linux-foundation.org,
	tytso@mit.edu, viro@zeniv.linux.org.uk, wangqing@vivo.com,
	yzaikin@google.com
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH] Fix regression due to "fs: move binfmt_misc sysctl to its own file"
Date: Mon, 7 Feb 2022 14:27:28 +0100	[thread overview]
Message-ID: <YgEeQNdgBuHRyEWl@dumbo> (raw)
In-Reply-To: <20220122061228.nmuo75sDn%akpm@linux-foundation.org>

Commit 3ba442d5331f did not go unnoticed, binfmt-support stopped to
work on my Debian system since v5.17-rc2 (did not check with -rc1).

The existance of /proc/sys/fs/binfmt_misc is a precondition for
attempting to mount the binfmt_misc fs, which in turn triggers the
autoload of the binfmt_misc module. Without it, no module is loaded
and no binfmt is available at boot.

Building as built-in or manually loading the module and mounting the fs
works fine, it's therefore only a matter of interaction with user-space.

I could try to improve the Debian systemd configuration but I can't
say anything about the other distributions.

In the meanwhile this patch restores a working system right after boot.

Fixes: 3ba442d5331f ("fs: move binfmt_misc sysctl to its own file")
Signed-off-by: Domenico Andreoli <domenico.andreoli@linux.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Antti Palosaari <crope@iki.fi>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Clemens Ladisch <clemens@ladisch.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: James E.J. Bottomley <jejb@linux.ibm.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Julia Lawall <julia.lawall@inria.fr>
Cc: Kees Cook <keescook@chromium.org>
Cc: Lukas Middendorf <kernel@tuxforce.de>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Phillip Potter <phil@philpotter.co.uk>
Cc: Qing Wang <wangqing@vivo.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Xiaoming Ni <nixiaoming@huawei.com>

---
 fs/binfmt_misc.c |    6 +-----
 kernel/sysctl.c  |   13 +++++++++++++
 2 files changed, 14 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/kernel/sysctl.c
===================================================================
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2806,6 +2806,17 @@ static struct ctl_table vm_table[] = {
 	{ }
 };
 
+static struct ctl_table fs_table[] = {
+#if defined(CONFIG_BINFMT_MISC) || defined(CONFIG_BINFMT_MISC_MODULE)
+	{
+		.procname	= "binfmt_misc",
+		.mode		= 0555,
+		.child		= sysctl_mount_point,
+	},
+#endif
+	{ }
+};
+
 static struct ctl_table debug_table[] = {
 #ifdef CONFIG_SYSCTL_EXCEPTION_TRACE
 	{
@@ -2825,6 +2836,7 @@ static struct ctl_table dev_table[] = {
 
 DECLARE_SYSCTL_BASE(kernel, kern_table);
 DECLARE_SYSCTL_BASE(vm, vm_table);
+DECLARE_SYSCTL_BASE(fs, fs_table);
 DECLARE_SYSCTL_BASE(debug, debug_table);
 DECLARE_SYSCTL_BASE(dev, dev_table);
 
@@ -2832,6 +2844,7 @@ int __init sysctl_init_bases(void)
 {
 	register_sysctl_base(kernel);
 	register_sysctl_base(vm);
+	register_sysctl_base(fs);
 	register_sysctl_base(debug);
 	register_sysctl_base(dev);
 

       reply	other threads:[~2022-02-07 13:52 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20220121221021.60533b009c357d660791476e@linux-foundation.org>
     [not found] ` <20220122061228.nmuo75sDn%akpm@linux-foundation.org>
2022-02-07 13:27   ` Domenico Andreoli [this message]
2022-02-07 21:46     ` Luis Chamberlain
2022-02-07 22:53       ` Tong Zhang
2022-02-08 17:20         ` Luis Chamberlain
2022-02-09  7:31           ` Domenico Andreoli
2022-02-09  7:49           ` [PATCH v2] " Domenico Andreoli
2022-02-09  7:55             ` Tong Zhang
2022-02-13 15:34             ` Ido Schimmel
2022-02-13 21:10               ` Tong Zhang
2022-02-14  7:47                 ` Ido Schimmel
2022-02-08  6:46     ` [PATCH] " Thorsten Leemhuis

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