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Date:   Sat, 28 Aug 2021 02:47:03 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Suren Baghdasaryan <surenb@google.com>
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Subject: Re: [PATCH v8 2/3] mm: add a field to store names for private
 anonymous memory
Message-ID: <YSmVl+DEPrU6oUR4@casper.infradead.org>
References: <20210827191858.2037087-1-surenb@google.com>
 <20210827191858.2037087-3-surenb@google.com>
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On Fri, Aug 27, 2021 at 12:18:57PM -0700, Suren Baghdasaryan wrote:
> +		anon_name = vma_anon_name(vma);
> +		if (anon_name) {
> +			seq_pad(m, ' ');
> +			seq_puts(m, "[anon:");
> +			seq_write(m, anon_name, strlen(anon_name));
> +			seq_putc(m, ']');
> +		}

...

> +	case PR_SET_VMA_ANON_NAME:
> +		name = strndup_user((const char __user *)arg,
> +				    ANON_VMA_NAME_MAX_LEN);
> +
> +		if (IS_ERR(name))
> +			return PTR_ERR(name);
> +
> +		for (pch = name; *pch != '\0'; pch++) {
> +			if (!isprint(*pch)) {
> +				kfree(name);
> +				return -EINVAL;

I think isprint() is too weak a check.  For example, I would suggest
forbidding the following characters: ':', ']', '[', ' '.  Perhaps
isalnum() would be better?  (permit a-zA-Z0-9)  I wouldn't necessarily
be opposed to some punctuation characters, but let's avoid creating
confusion.  Do you happen to know which characters are actually in use
today?