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Date:   Thu, 20 Oct 2022 17:14:13 +0200
From:   Petr Vorel <pvorel@suse.cz>
To:     linux-kernel@vger.kernel.org
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Torsten Hilbrich <torsten.hilbrich@secunet.com>
Subject: Re: [PATCH 1/1] kernel/utsname_sysctl.c: Add missing enum uts_proc
 value
Message-ID: <Y1FlxYr9IF7Phy1u@pevik>
Reply-To: Petr Vorel <pvorel@suse.cz>
References: <20221020150645.11719-1-pvorel@suse.cz>
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Hi all,

[ Cc regressions@lists.linux.dev ]

Kind regards,
Petr

> bfca3dd3d068 added new struct ctl_table uts_kern_table[], but not new
> enum uts_proc value. It broke the notification mechanism between the
> sethostname syscall and the pollers of /proc/sys/kernel/hostname.

> The table uts_kern_table is addressed within uts_proc_notify by the enum
> value, that's why new enum value is needed.

> Fixes: bfca3dd3d068 ("kernel/utsname_sysctl.c: print kernel arch")

> Reported-by: Torsten Hilbrich <torsten.hilbrich@secunet.com>
> Signed-off-by: Petr Vorel <pvorel@suse.cz>
> ---
> Hi all,

> I'm sorry to introduce a regression.

> Torsten Hilbrich reported [1] that hostnamectl set-hostname foo
> which does poll() got affected by bfca3dd3d068. He also wrote a
> reproducer [2] which does not require systemd, I tested the patch on
> dracut initramfs.

> Kind regards,
> Petr

> [1] https://lore.kernel.org/lkml/0c2b92a6-0f25-9538-178f-eee3b06da23f@secunet.com/
> [2] https://lore.kernel.org/lkml/ec9e00b9-8b47-7918-c39b-8b0069003169@secunet.com/2-hostname-poll-test.c

>  include/linux/utsname.h | 1 +
>  1 file changed, 1 insertion(+)

> diff --git a/include/linux/utsname.h b/include/linux/utsname.h
> index 2b1737c9b244..bf7613ba412b 100644
> --- a/include/linux/utsname.h
> +++ b/include/linux/utsname.h
> @@ -10,6 +10,7 @@
>  #include <uapi/linux/utsname.h>

>  enum uts_proc {
> +	UTS_PROC_ARCH,
>  	UTS_PROC_OSTYPE,
>  	UTS_PROC_OSRELEASE,
>  	UTS_PROC_VERSION,