linux-kernel - Re: [PATCH 2/2] Revert "pstore: Honor dmesg

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Date:   Wed, 16 Aug 2017 16:59:22 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org, Nick Kralevich <nnk@...gle.com>,
        Sebastian Schmidt <yath@...h.de>,
        Tony Luck <tony.luck@...el.com>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Patrick Tjin <pattjin@...gle.com>,
        Mark Salyzyn <salyzyn@...gle.com>
Subject: Re: [PATCH 2/2] Revert "pstore: Honor dmesg_restrict sysctl on dmesg
 dumps"

On (08/10/17 13:36), Kees Cook wrote:
[..]
> -static int pstore_check_syslog_permissions(struct pstore_private *ps)
> -{
> -	switch (ps->record->type) {
> -	case PSTORE_TYPE_DMESG:
> -	case PSTORE_TYPE_CONSOLE:
> -		return check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
> -			SYSLOG_FROM_READER);
> -	default:
> -		return 0;
> -	}
> -}
> -
>  static ssize_t pstore_file_read(struct file *file, char __user *userbuf,
>  						size_t count, loff_t *ppos)
>  {
> @@ -163,10 +150,6 @@ static int pstore_file_open(struct inode *inode, struct file *file)
>  	int err;
>  	const struct seq_operations *sops = NULL;
>  
> -	err = pstore_check_syslog_permissions(ps);
> -	if (err)
> -		return err;
> -
>  	if (ps->record->type == PSTORE_TYPE_FTRACE)
>  		sops = &pstore_ftrace_seq_ops;
>  
> @@ -204,11 +187,6 @@ static int pstore_unlink(struct inode *dir, struct dentry *dentry)
>  {
>  	struct pstore_private *p = d_inode(dentry)->i_private;
>  	struct pstore_record *record = p->record;
> -	int err;
> -
> -	err = pstore_check_syslog_permissions(p);
> -	if (err)
> -		return err;

it's hard to review security related patches :)

so, effectively, `dmesg_restrict' does not work for pstore anymore? wouldn't
that be a problem? one more thing, doesn't it affect the consistency -- we
respect the `dmesg_restrict' restrictions, except that we ignore it when
access pstore? or do I completely misunderstand the change? sorry if so.

	-ss