linux-kernel - Re: [Y2038] [PATCH 04/20] mount: Add mount warning for impending timestamp expiry

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Date:   Mon, 05 Aug 2019 15:12:41 +0100
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Deepa Dinamani <deepa.kernel@...il.com>, viro@...iv.linux.org.uk,
        linux-kernel@...r.kernel.org
Cc:     linux-fsdevel@...r.kernel.org, y2038@...ts.linaro.org,
        arnd@...db.de
Subject: Re: [Y2038] [PATCH 04/20] mount: Add mount warning for impending
 timestamp expiry

On Mon, 2019-07-29 at 18:49 -0700, Deepa Dinamani wrote:
> The warning reuses the uptime max of 30 years used by the
> setitimeofday().
> 
> Note that the warning is only added for new filesystem mounts
> through the mount syscall. Automounts do not have the same warning.
> 
> Signed-off-by: Deepa Dinamani <deepa.kernel@...il.com>
> ---
>  fs/namespace.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/fs/namespace.c b/fs/namespace.c
> index b26778bdc236..5314fac8035e 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -2739,6 +2739,17 @@ static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint,
>  	error = do_add_mount(real_mount(mnt), mountpoint, mnt_flags);
>  	if (error < 0)
>  		mntput(mnt);
> +
> +	if (!error && sb->s_time_max &&

I don't know why you are testing sb->s_time_max here - it should always
be non-zero since alloc_super() sets it to TIME64_MAX.

> +	    (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) {
> +		char *buf = (char *)__get_free_page(GFP_KERNEL);
> +		char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(-ENOMEM);
> +
> +		pr_warn("Mounted %s file system at %s supports timestamps until 0x%llx\n",
> +			fc->fs_type->name, mntpath, (unsigned long long)sb->s_time_max);

This doesn't seem like a helpful way to log the time.  Maybe use
time64_to_tm() to convert to "broken down" time and then print it with
"%ptR"... but that wants struct rtc_time.  If you apply the attached
patch, however, you should then be able to print struct tm with
"%ptT".

Ben.

> +		free_page((unsigned long)buf);
> +	}
> +
>  	return error;
>  }
>  
-- 
Ben Hutchings, Software Developer                         Codethink Ltd
https://www.codethink.co.uk/                 Dale House, 35 Dale Street
                                     Manchester, M1 2HF, United Kingdom

View attachment "0001-vsprintf-Add-support-for-printing-struct-tm-in-human.patch" of type "text/x-patch" (3926 bytes)