linux-kernel - [PATCH 1/4] lib/strn*,objtool: Enforce user_access

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Message-ID: <20220408094718.262932488@infradead.org>
Date:   Fri, 08 Apr 2022 11:45:53 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        rick.p.edgecombe@...el.com, jpoimboe@...hat.com,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 1/4] lib/strn*,objtool: Enforce user_access_begin() rules

Apparently GCC can fail to inline a 'static inline' single caller
function:

  lib/strnlen_user.o: warning: objtool: strnlen_user()+0x33: call to do_strnlen_user() with UACCESS enabled
  lib/strncpy_from_user.o: warning: objtool: strncpy_from_user()+0x33: call to do_strncpy_from_user() with UACCESS enabled

Reported-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 lib/strncpy_from_user.c |    2 +-
 lib/strnlen_user.c      |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -25,7 +25,7 @@
  * hit it), 'max' is the address space maximum (and we return
  * -EFAULT if we hit it).
  */
-static inline long do_strncpy_from_user(char *dst, const char __user *src,
+static __always_inline long do_strncpy_from_user(char *dst, const char __user *src,
 					unsigned long count, unsigned long max)
 {
 	const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
--- a/lib/strnlen_user.c
+++ b/lib/strnlen_user.c
@@ -20,7 +20,7 @@
  * if it fits in a aligned 'long'. The caller needs to check
  * the return value against "> max".
  */
-static inline long do_strnlen_user(const char __user *src, unsigned long count, unsigned long max)
+static __always_inline long do_strnlen_user(const char __user *src, unsigned long count, unsigned long max)
 {
 	const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
 	unsigned long align, res = 0;