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 <[email protected]>
---
v5:
- Removed net/core/scm.c which is converted to scope user access by previous 
patch
- Renamed the patch as it now only handles lib/strncpy_from_user.c and 
lib/strnlen_user.c

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 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

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


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