linux-kernel - [PATCH 1/5] uaccess: Add masked_user_{read/write}_access

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Message-ID: <6fddae0cf0da15a6521bb847b63324b7a2a067b1.1750585239.git.christophe.leroy@csgroup.eu>
Date: Sun, 22 Jun 2025 11:52:39 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Naveen N Rao <naveen@...nel.org>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Jan Kara <jack@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Darren Hart <dvhart@...radead.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	"Andre Almeida" <andrealmeid@...lia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Laight <david.laight.linux@...il.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH 1/5] uaccess: Add masked_user_{read/write}_access_begin

Allthough masked_user_access_begin() seems to only be used when reading
data from user at the moment, introduce masked_user_read_access_begin()
and masked_user_write_access_begin() in order to match
user_read_access_begin() and user_write_access_begin().

Have them default to masked_user_access_begin() when they are
not defined.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 fs/select.c             | 2 +-
 include/linux/uaccess.h | 8 ++++++++
 kernel/futex/futex.h    | 4 ++--
 lib/strncpy_from_user.c | 2 +-
 lib/strnlen_user.c      | 2 +-
 5 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/fs/select.c b/fs/select.c
index 9fb650d03d52..d8547bedf5eb 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -777,7 +777,7 @@ static inline int get_sigset_argpack(struct sigset_argpack *to,
 	// the path is hot enough for overhead of copy_from_user() to matter
 	if (from) {
 		if (can_do_masked_user_access())
-			from = masked_user_access_begin(from);
+			from = masked_user_read_access_begin(from);
 		else if (!user_read_access_begin(from, sizeof(*from)))
 			return -EFAULT;
 		unsafe_get_user(to->p, &from->p, Efault);
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 7c06f4795670..682a0cd2fe51 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -41,6 +41,14 @@
  #define mask_user_address(src) (src)
 #endif
 
+#ifndef masked_user_write_access_begin
+#define masked_user_write_access_begin masked_user_access_begin
+#endif
+#ifndef masked_user_read_access_begin
+#define masked_user_read_access_begin masked_user_access_begin
+#endif
+
+
 /*
  * Architectures should provide two primitives (raw_copy_{to,from}_user())
  * and get rid of their private instances of copy_{to,from}_user() and
diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index fcd1617212ee..6cfcafa00736 100644
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -305,7 +305,7 @@ static __always_inline int futex_get_value(u32 *dest, u32 __user *from)
 	u32 val;
 
 	if (can_do_masked_user_access())
-		from = masked_user_access_begin(from);
+		from = masked_user_read_access_begin(from);
 	else if (!user_read_access_begin(from, sizeof(*from)))
 		return -EFAULT;
 	unsafe_get_user(val, from, Efault);
@@ -320,7 +320,7 @@ static __always_inline int futex_get_value(u32 *dest, u32 __user *from)
 static __always_inline int futex_put_value(u32 val, u32 __user *to)
 {
 	if (can_do_masked_user_access())
-		to = masked_user_access_begin(to);
+		to = masked_user_read_access_begin(to);
 	else if (!user_read_access_begin(to, sizeof(*to)))
 		return -EFAULT;
 	unsafe_put_user(val, to, Efault);
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index 6dc234913dd5..5bb752ff7c61 100644
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -126,7 +126,7 @@ long strncpy_from_user(char *dst, const char __user *src, long count)
 	if (can_do_masked_user_access()) {
 		long retval;
 
-		src = masked_user_access_begin(src);
+		src = masked_user_read_access_begin(src);
 		retval = do_strncpy_from_user(dst, src, count, count);
 		user_read_access_end();
 		return retval;
diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
index 6e489f9e90f1..4a6574b67f82 100644
--- a/lib/strnlen_user.c
+++ b/lib/strnlen_user.c
@@ -99,7 +99,7 @@ long strnlen_user(const char __user *str, long count)
 	if (can_do_masked_user_access()) {
 		long retval;
 
-		str = masked_user_access_begin(str);
+		str = masked_user_read_access_begin(str);
 		retval = do_strnlen_user(str, count, count);
 		user_read_access_end();
 		return retval;
-- 
2.49.0