linux-kernel - [PATCH] uaccess: gate _copy_[to|from]_user on !INLINE_COPY_FROM

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Message-ID: <20251118173250.2821388-1-aliceryhl@google.com>
Date: Tue, 18 Nov 2025 17:32:50 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: akpm@...ux-foundation.org
Cc: a.hindborg@...nel.org, alex.gaynor@...il.com, aliceryhl@...gle.com, 
	arnd@...db.de, bjorn3_gh@...tonmail.com, boqun.feng@...il.com, 
	dakr@...nel.org, gary@...yguo.net, jhubbard@...dia.com, 
	linux-kernel@...r.kernel.org, lossin@...nel.org, ojeda@...nel.org, 
	rust-for-linux@...r.kernel.org, tmgross@...ch.edu, yury.norov@...il.com
Subject: [PATCH] uaccess: gate _copy_[to|from]_user on !INLINE_COPY_FROM_USER

These methods only exist when INLINE_COPY_FROM_USER is disabled, so
update the header file to reflect that.

This fixes the following error on builds that enable both RUST and
INLINE_COPY_FROM_USER.

ERROR: modpost: "_copy_from_user" [samples/rust/rust_misc_device.ko] undefined!
ERROR: modpost: "_copy_to_user" [samples/rust/rust_misc_device.ko] undefined!

This error is triggered because when a method is available both as a
rust_helper_* and normal method, Rust will call the normal method.

Fixes: d99dc586ca7c ("uaccess: decouple INLINE_COPY_FROM_USER and CONFIG_RUST")
Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
---
 include/linux/uaccess.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 01cbd7dd0ba3..205e1e65f481 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -181,8 +181,10 @@ _inline_copy_from_user(void *to, const void __user *from, unsigned long n)
 	memset(to + (n - res), 0, res);
 	return res;
 }
+#ifndef INLINE_COPY_FROM_USER
 extern __must_check unsigned long
 _copy_from_user(void *, const void __user *, unsigned long);
+#endif
 
 static inline __must_check unsigned long
 _inline_copy_to_user(void __user *to, const void *from, unsigned long n)
@@ -196,8 +198,10 @@ _inline_copy_to_user(void __user *to, const void *from, unsigned long n)
 	}
 	return n;
 }
+#ifndef INLINE_COPY_FROM_USER
 extern __must_check unsigned long
 _copy_to_user(void __user *, const void *, unsigned long);
+#endif
 
 static __always_inline unsigned long __must_check
 copy_from_user(void *to, const void __user *from, unsigned long n)

base-commit: 3e4b89e970365db7fe2c4171be06c0e88e3bcbe6
-- 
2.52.0.rc1.455.g30608eb744-goog