linux-kernel - [PATCH AUTOSEL 4.4 26/92] mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on older GCC versions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20190522193127.27079-26-sashal@kernel.org>
Date:   Wed, 22 May 2019 15:30:21 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>, luto@...nel.org,
        Ingo Molnar <mingo@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.4 26/92] mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on older GCC versions

From: Peter Zijlstra <peterz@...radead.org>

[ Upstream commit 29da93fea3ea39ab9b12270cc6be1b70ef201c9e ]

Randy reported objtool triggered on his (GCC-7.4) build:

  lib/strncpy_from_user.o: warning: objtool: strncpy_from_user()+0x315: call to __ubsan_handle_add_overflow() with UACCESS enabled
  lib/strnlen_user.o: warning: objtool: strnlen_user()+0x337: call to __ubsan_handle_sub_overflow() with UACCESS enabled

This is due to UBSAN generating signed-overflow-UB warnings where it
should not. Prior to GCC-8 UBSAN ignored -fwrapv (which the kernel
uses through -fno-strict-overflow).

Make the functions use 'unsigned long' throughout.

Reported-by: Randy Dunlap <rdunlap@...radead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Randy Dunlap <rdunlap@...radead.org> # build-tested
Acked-by: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: luto@...nel.org
Link: http://lkml.kernel.org/r/20190424072208.754094071@infradead.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 lib/strncpy_from_user.c | 5 +++--
 lib/strnlen_user.c      | 4 ++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index e0af6ff73d146..f8b1e3cb716b9 100644
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -20,10 +20,11 @@
  * 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, long count, unsigned long max)
+static 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;
-	long res = 0;
+	unsigned long res = 0;
 
 	/*
 	 * Truncate 'max' to the user-specified limit, so that
diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
index 3a5f2b366d84e..1c87bfa63db7f 100644
--- a/lib/strnlen_user.c
+++ b/lib/strnlen_user.c
@@ -27,7 +27,7 @@
 static 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;
-	long align, res = 0;
+	unsigned long align, res = 0;
 	unsigned long c;
 
 	/*
@@ -41,7 +41,7 @@ static inline long do_strnlen_user(const char __user *src, unsigned long count,
 	 * Do everything aligned. But that means that we
 	 * need to also expand the maximum..
 	 */
-	align = (sizeof(long) - 1) & (unsigned long)src;
+	align = (sizeof(unsigned long) - 1) & (unsigned long)src;
 	src -= align;
 	max += align;
 
-- 
2.20.1