Properly use masked_user_read_access_begin() and
masked_user_write_access_begin() instead of masked_user_access_begin()
in order to match user_read_access_end() and user_write_access_end().
This is important for architectures like powerpc that enable
separately user reads and user writes.

That means masked_user_read_access_begin() is used when user memory is
exclusively read during the window and masked_user_write_access_begin()
is used when user memory is exclusively writen during the window.
masked_user_access_begin() remains and is used when both reads and
writes are performed during the open window. Each of them is expected
to be terminated by the matching user_read_access_end(),
user_write_access_end() and user_access_end().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v4: Rebased on top of core-scoped-uaccess tag

v3: Rebased on top of v6.18-rc1 ==> change in net/core/scm.c

v2: Added more explanations in the commit message following comments received.
---
 lib/strncpy_from_user.c | 2 +-
 lib/strnlen_user.c      | 2 +-
 net/core/scm.c          | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index 6dc234913dd58..5bb752ff7c61b 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 6e489f9e90f15..4a6574b67f824 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;
diff --git a/net/core/scm.c b/net/core/scm.c
index 66eaee783e8be..4a65f9baa87e7 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -274,7 +274,7 @@ int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
 		check_object_size(data, cmlen - sizeof(*cm), true);
 
 		if (can_do_masked_user_access())
-			cm = masked_user_access_begin(cm);
+			cm = masked_user_write_access_begin(cm);
 		else if (!user_write_access_begin(cm, cmlen))
 			goto efault;
 
-- 
2.49.0