+ x86-asm-make-sure-__put_user_size-evaluates-pointer-once.patch added to mm-hotfixes-unstable branch

+ x86-asm-make-sure-__put_user_size-evaluates-pointer-once.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: x86: asm: make sure __put_user_size() evaluates pointer once
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     x86-asm-make-sure-__put_user_size-evaluates-pointer-once.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/x86-asm-make-sure-__put_user_size-evaluates-pointer-once.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Alexander Potapenko <glider@google.com>
Subject: x86: asm: make sure __put_user_size() evaluates pointer once
Date: Mon, 24 Oct 2022 23:21:43 +0200

User access macros must ensure their arguments are evaluated only once if
they are used more than once in the macro body.  Adding
instrument_put_user() to __put_user_size() resulted in double evaluation
of the `ptr` argument, which led to correctness issues when performing
e.g.  unsafe_put_user(..., p++, ...).

To fix those issues, evaluate the `ptr` argument of __put_user_size() at
the beginning of the macro.

Link: https://lkml.kernel.org/r/20221024212144.2852069-4-glider@google.com
Fixes: 888f84a6da4d ("x86: asm: instrument usercopy in get_user() and put_user()")
Signed-off-by: Alexander Potapenko <glider@google.com>
Reported-by: youling257 <youling257@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/x86/include/asm/uaccess.h |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

--- a/arch/x86/include/asm/uaccess.h~x86-asm-make-sure-__put_user_size-evaluates-pointer-once
+++ a/arch/x86/include/asm/uaccess.h
@@ -254,24 +254,25 @@ extern void __put_user_nocheck_8(void);
 #define __put_user_size(x, ptr, size, label)				\
 do {									\
 	__typeof__(*(ptr)) __x = (x); /* eval x once */			\
-	__chk_user_ptr(ptr);						\
+	__typeof__(ptr) __ptr = (ptr); /* eval ptr once */		\
+	__chk_user_ptr(__ptr);						\
 	switch (size) {							\
 	case 1:								\
-		__put_user_goto(__x, ptr, "b", "iq", label);		\
+		__put_user_goto(__x, __ptr, "b", "iq", label);		\
 		break;							\
 	case 2:								\
-		__put_user_goto(__x, ptr, "w", "ir", label);		\
+		__put_user_goto(__x, __ptr, "w", "ir", label);		\
 		break;							\
 	case 4:								\
-		__put_user_goto(__x, ptr, "l", "ir", label);		\
+		__put_user_goto(__x, __ptr, "l", "ir", label);		\
 		break;							\
 	case 8:								\
-		__put_user_goto_u64(__x, ptr, label);			\
+		__put_user_goto_u64(__x, __ptr, label);			\
 		break;							\
 	default:							\
 		__put_user_bad();					\
 	}								\
-	instrument_put_user(__x, ptr, size);				\
+	instrument_put_user(__x, __ptr, size);				\
 } while (0)
 
 #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
_

Patches currently in -mm which might be from glider@google.com are

mm-kmsan-export-kmsan_copy_page_meta.patch
x86-purgatory-disable-kmsan-instrumentation.patch
kconfigdebug-disable-config_frame_warn-for-kmsan-by-default.patch
x86-asm-make-sure-__put_user_size-evaluates-pointer-once.patch
x86-fortify-kmsan-fix-kmsan-fortify-builds.patch