linux-hardening - [RFC v1 10/17] iov_iter: add SafeFetch pinning call to copy_from_user

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Message-Id: <20250712192202.707192-11-gatlin.newhouse@gmail.com>
Date: Sat, 12 Jul 2025 19:21:55 +0000
From: Gatlin Newhouse <gatlin.newhouse@...il.com>
To: linux-hardening@...r.kernel.org
Cc: Gatlin Newhouse <gatlin.newhouse@...il.com>
Subject: [RFC v1 10/17] iov_iter: add SafeFetch pinning call to copy_from_user_iter()

---
 lib/iov_iter.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index f9193f952f49..8997272481c3 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -41,6 +41,10 @@ size_t copy_to_user_iter_nofault(void __user *iter_to, size_t progress,
 	return res < 0 ? len : res;
 }
 
+#ifndef PIN_BUDDY_PAGES_WATERMARK
+#define PIN_BUDDY_PAGES_WATERMARK PAGE_SIZE
+#endif
+
 static __always_inline
 size_t copy_from_user_iter(void __user *iter_from, size_t progress,
 			   size_t len, void *to, void *priv2)
@@ -52,7 +56,15 @@ size_t copy_from_user_iter(void __user *iter_from, size_t progress,
 	if (access_ok(iter_from, len)) {
 		to += progress;
 		instrument_copy_from_user_before(to, iter_from, len);
+#ifdef SAFEFETCH_PIN_BUDDY_PAGES
+		/* #warning "Using Page_pinning for copyin calls" */
+		if (len >= PIN_BUDDY_PAGES_WATERMARK)
+			res = raw_copy_from_user_pinning(to, iter_from, len);
+		else
+			res = raw_copy_from_user(to, iter_from, len);
+#else
 		res = raw_copy_from_user(to, iter_from, len);
+#endif
 		instrument_copy_from_user_after(to, iter_from, len, res);
 	}
 	return res;
-- 
2.25.1