On Sat, Aug 28, 2021 at 02:47:03AM +0100, Matthew Wilcox wrote:

On Fri, Aug 27, 2021 at 12:18:57PM -0700, Suren Baghdasaryan wrote:

quoted

+		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, ']');
+		}

Maybe after seq_pad, use: seq_printf(m, "[anon:%s]", anon_name);

...

quoted

+	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?

There's some sense in refusing [, ], and :, but removing " " seems
unhelpful for reasonable descriptors. As long as weird stuff is escaped,
I think it's fine. Any parser can just extract with m|\[anon:(.*)\]$|

For example, just escape it here instead of refusing to take it. Something
like:

	name = strndup_user((const char __user *)arg,
			    ANON_VMA_NAME_MAX_LEN);
	escaped = kasprintf(GFP_KERNEL, "%pE", name);
	if (escaped) {
		kfree(name);
		return -ENOMEM;
	}
	kfree(name);
	name = escaped;

-- 
Kees Cook