Re: [PATCH] systemd: dont spew hidepid mount errors for kernels < v5.8

["Richard Purdie" <richard.purdie@linuxfoundation.org>]

On Fri, 2021-01-15 at 00:26 -0500, Paul Gortmaker wrote:
> Recent systemd started using ascii args to "hidepid=" mount options
> for proc fs - unconditionally -- even though kernels older than v5.8
> emit an error message on each attempt:
> 
> root@qemux86-64:~# cat /proc/version
> Linux version 5.4.87-yocto-standard (oe-user@oe-host) (gcc version 10.2.0 (GCC)) #1 SMP PREEMPT Fri Jan 8 01:47:13 UTC 2021
> root@qemux86-64:~# dmesg|grep proc:
> [   29.487995] proc: Bad value for 'hidepid'
> [   43.170571] proc: Bad value for 'hidepid'
> [   44.175615] proc: Bad value for 'hidepid'
> [   46.213300] proc: Bad value for 'hidepid'
> root@qemux86-64:~#
> 
> Simply ignoring them as the systemd maintainer unconditionally says
> is the resolution is clearly not acceptable, given the above.
> 
> Add a kernel version check to avoid calling mount with invalid args.
> Further details are within the enclosed systemd commit.
> 
> Cc: Luca Boccassi <luca.boccassi@microsoft.com>
> Cc: Richard Purdie <richard.purdie@linuxfoundation.org>
> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
> 
> diff --git a/meta/recipes-core/systemd/systemd/0027-proc-dont-trigger-mount-error-with-invalid-options-o.patch b/meta/recipes-core/systemd/systemd/0027-proc-dont-trigger-mount-error-with-invalid-options-o.patch
> new file mode 100644
> index 000000000000..65e7eca32d05
> --- /dev/null
> +++ b/meta/recipes-core/systemd/systemd/0027-proc-dont-trigger-mount-error-with-invalid-options-o.patch
> @@ -0,0 +1,126 @@
> +From 297aba739cd689e4dc9f43bb1422ec88d481099a Mon Sep 17 00:00:00 2001
> +From: Paul Gortmaker <paul.gortmaker@windriver.com>
> +Date: Wed, 13 Jan 2021 21:09:33 +0000
> +Subject: [PATCH] proc: dont trigger mount error with invalid options on old
> + kernels
> +
> +As of commit 4e39995371738b04d98d27b0d34ea8fe09ec9fab ("core: introduce
> +ProtectProc= and ProcSubset= to expose hidepid= and subset= procfs
> +mount options") kernels older than v5.8 generate multple warnings at
> +boot, as seen in this Yocto build from today:
> +
> +     qemux86-64 login: root
> +     [   65.829009] proc: Bad value for 'hidepid'
> +     root@qemux86-64:~# dmesg|grep proc:
> +     [   16.990706] proc: Bad value for 'hidepid'
> +     [   28.060178] proc: Bad value for 'hidepid'
> +     [   28.874229] proc: Bad value for 'hidepid'
> +     [   32.685107] proc: Bad value for 'hidepid'
> +     [   65.829009] proc: Bad value for 'hidepid'
> +     root@qemux86-64:~#
> +
> +The systemd maintainer has dismissed this as something people should
> +simply ignore[1] and has no interest in trying to avoid it by
> +proactively checking the kernel version, so people can safely assume
> +that they will never see this version check commit upstream.
> +
> +However, as can be seen above, telling people to just ignore it is not
> +an option, as we'll end up answering the same question and dealing with
> +the same bug over and over again.
> +
> +The commit that triggers this is systemd v247-rc1~378^2~3 -- so any
> +systemd 247 and above plus kernel v5.7 or older will need this.
> +
> +[1] https://github.com/systemd/systemd/issues/16896
> +
> +Upstream-Status: Actively hostile

The status needs to be

Upstream-Status: Denied [Actively hostile https://github.com/systemd/systemd/issues/16896]

(so our tools have an idea of what status patches are in)

https://wiki.yoctoproject.org/wiki/Best_Known_Methods_(BKMs)_for_Package_Updating#Patch_Comments

Cheers,

Richard