blob: 5e1427c4e7c0642ff80be0bc84f0d622c98d2013 [file] [log] [blame]
From bb6c9769665d1cfeb8e933c77559ba2ba61d025d Mon Sep 17 00:00:00 2001
From: Christophe Leroy <christophe.leroy@c-s.fr>
Date: Thu, 23 Jan 2020 08:34:18 +0000
Subject: [PATCH] lib: Reduce user_access_begin() boundaries in
strncpy_from_user() and strnlen_user()
commit ab10ae1c3bef56c29bac61e1201c752221b87b41 upstream.
The range passed to user_access_begin() by strncpy_from_user() and
strnlen_user() starts at 'src' and goes up to the limit of userspace
although reads will be limited by the 'count' param.
On 32 bits powerpc (book3s/32) access has to be granted for each
256Mbytes segment and the cost increases with the number of segments to
unlock.
Limit the range with 'count' param.
Fixes: 594cc251fdd0 ("make 'user_access_begin()' do 'access_ok()'")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index 023ba9f3b99f..10af8be1cace 100644
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -29,13 +29,6 @@ static inline long do_strncpy_from_user(char *dst, const char __user *src,
const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
unsigned long res = 0;
- /*
- * Truncate 'max' to the user-specified limit, so that
- * we only have one limit we need to check in the loop
- */
- if (max > count)
- max = count;
-
if (IS_UNALIGNED(src, dst))
goto byte_at_a_time;
@@ -113,6 +106,13 @@ long strncpy_from_user(char *dst, const char __user *src, long count)
unsigned long max = max_addr - src_addr;
long retval;
+ /*
+ * Truncate 'max' to the user-specified limit, so that
+ * we only have one limit we need to check in the loop
+ */
+ if (max > count)
+ max = count;
+
kasan_check_write(dst, count);
check_object_size(dst, count, false);
if (user_access_begin(src, max)) {
diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
index 7f2db3fe311f..069fc8e463d0 100644
--- a/lib/strnlen_user.c
+++ b/lib/strnlen_user.c
@@ -32,13 +32,6 @@ static inline long do_strnlen_user(const char __user *src, unsigned long count,
unsigned long c;
/*
- * Truncate 'max' to the user-specified limit, so that
- * we only have one limit we need to check in the loop
- */
- if (max > count)
- max = count;
-
- /*
* Do everything aligned. But that means that we
* need to also expand the maximum..
*/
@@ -114,6 +107,13 @@ long strnlen_user(const char __user *str, long count)
unsigned long max = max_addr - src_addr;
long retval;
+ /*
+ * Truncate 'max' to the user-specified limit, so that
+ * we only have one limit we need to check in the loop
+ */
+ if (max > count)
+ max = count;
+
if (user_access_begin(str, max)) {
retval = do_strnlen_user(str, count, max);
user_access_end();
--
2.7.4