[PATCH v3 04/10] powerpc/uaccess: Move barrier_nospec() out of allow_read_{from/write}_user()
From: Christophe Leroy <hidden>
Date: 2025-10-17 10:50:36
Also in:
linux-block, linux-fsdevel, lkml, netdev
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
Commit 74e19ef0ff80 ("uaccess: Add speculation barrier to
copy_from_user()") added a redundant barrier_nospec() in
copy_from_user(), because powerpc is already calling
barrier_nospec() in allow_read_from_user() and
allow_read_write_user(). But on other architectures that
call to barrier_nospec() was missing. So change powerpc
instead of reverting the above commit and having to fix
other architectures one by one. This is now possible
because barrier_nospec() has also been added in
copy_from_user_iter().
Move barrier_nospec() out of allow_read_from_user() and
allow_read_write_user(). This will also allow reuse of those
functions when implementing masked user access which doesn't
require barrier_nospec().
Don't add it back in raw_copy_from_user() as it is already called
by copy_from_user() and copy_from_user_iter().
Fixes: 74e19ef0ff80 ("uaccess: Add speculation barrier to copy_from_user()")
Signed-off-by: Christophe Leroy <redacted>
---
arch/powerpc/include/asm/kup.h | 2 --
arch/powerpc/include/asm/uaccess.h | 4 ++++
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h
index dab63b82a8d4f..f2009d7c8cfa7 100644
--- a/arch/powerpc/include/asm/kup.h
+++ b/arch/powerpc/include/asm/kup.h@@ -134,7 +134,6 @@ static __always_inline void kuap_assert_locked(void) static __always_inline void allow_read_from_user(const void __user *from, unsigned long size) { - barrier_nospec(); allow_user_access(NULL, from, size, KUAP_READ); }
@@ -146,7 +145,6 @@ static __always_inline void allow_write_to_user(void __user *to, unsigned long s static __always_inline void allow_read_write_user(void __user *to, const void __user *from, unsigned long size) { - barrier_nospec(); allow_user_access(to, from, size, KUAP_READ_WRITE); }
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 4f5a46a77fa2b..3987a5c33558b 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h@@ -301,6 +301,7 @@ do { \ __typeof__(sizeof(*(ptr))) __gu_size = sizeof(*(ptr)); \ \ might_fault(); \ + barrier_nospec(); \ allow_read_from_user(__gu_addr, __gu_size); \ __get_user_size_allowed(__gu_val, __gu_addr, __gu_size, __gu_err); \ prevent_read_from_user(__gu_addr, __gu_size); \
@@ -329,6 +330,7 @@ raw_copy_in_user(void __user *to, const void __user *from, unsigned long n) { unsigned long ret; + barrier_nospec(); allow_read_write_user(to, from, n); ret = __copy_tofrom_user(to, from, n); prevent_read_write_user(to, from, n);
@@ -415,6 +417,7 @@ static __must_check __always_inline bool user_access_begin(const void __user *pt might_fault(); + barrier_nospec(); allow_read_write_user((void __user *)ptr, ptr, len); return true; }
@@ -431,6 +434,7 @@ user_read_access_begin(const void __user *ptr, size_t len) might_fault(); + barrier_nospec(); allow_read_from_user(ptr, len); return true; }
--
2.49.0