linux-kernel - [PATCH v3 2/5] uaccess: Use user_access_ok() in user_access

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Message-Id: <155127859433.32576.17845647712461950214.stgit@devbox>
Date:   Wed, 27 Feb 2019 23:43:14 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     mhiramat@...nel.org, linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Changbin Du <changbin.du@...il.com>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Nadav Amit <namit@...are.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH v3 2/5] uaccess: Use user_access_ok() in user_access_begin()

Use user_access_ok() instead of access_ok() in user_access_begin()
to validate the access context is user. This also allow us to
use (generic) strncpy_from_user() and strnlen_user() in atomic
state with setting USER_DS and disable pagefaults.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 arch/x86/include/asm/uaccess.h |    2 +-
 include/linux/uaccess.h        |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 3125d129d3b6..3b7502a34114 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -715,7 +715,7 @@ extern struct movsl_mask {
  */
 static __must_check inline bool user_access_begin(const void __user *ptr, size_t len)
 {
-	if (unlikely(!access_ok(ptr,len)))
+	if (unlikely(!user_access_ok(ptr, len)))
 		return 0;
 	__uaccess_begin_nospec();
 	return 1;
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index bf762689658b..1afd9dfabe67 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -282,7 +282,7 @@ extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
 	probe_kernel_read(&retval, addr, sizeof(retval))
 
 #ifndef user_access_begin
-#define user_access_begin(ptr,len) access_ok(ptr, len)
+#define user_access_begin(ptr, len) user_access_ok(ptr, len)
 #define user_access_end() do { } while (0)
 #define unsafe_get_user(x, ptr, err) do { if (unlikely(__get_user(x, ptr))) goto err; } while (0)
 #define unsafe_put_user(x, ptr, err) do { if (unlikely(__put_user(x, ptr))) goto err; } while (0)