The patch titled
Subject: lib: reduce user_access_begin() boundaries in strncpy_from_user() and strnlen_user()
has been added to the -mm tree. Its filename is
lib-reduce-user_access_begin-boundaries-in-strncpy_from_user-and-strnlen_user.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lib-reduce-user_access_begin-boundaries-in-strncpy_from_user-and-strnlen_user.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lib-reduce-user_access_begin-boundaries-in-strncpy_from_user-and-strnlen_user.patch
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------------------------------------------------------
From: Christophe Leroy <christophe.leroy@xxxxxx>
Subject: lib: reduce user_access_begin() boundaries in strncpy_from_user() and strnlen_user()
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
allthough 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.
Link: http://lkml.kernel.org/r/70f99f7474826883877e84f93224e937d9c974de.1579767339.git.christophe.leroy@xxxxxx
Fixes: 594cc251fdd0 ("make 'user_access_begin()' do 'access_ok()'")
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
Acked-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/strncpy_from_user.c | 14 +++++++-------
lib/strnlen_user.c | 14 +++++++-------
2 files changed, 14 insertions(+), 14 deletions(-)
--- a/lib/strncpy_from_user.c~lib-reduce-user_access_begin-boundaries-in-strncpy_from_user-and-strnlen_user
+++ a/lib/strncpy_from_user.c
@@ -30,13 +30,6 @@ static inline long do_strncpy_from_user(
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;
@@ -114,6 +107,13 @@ long strncpy_from_user(char *dst, const
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)) {
--- a/lib/strnlen_user.c~lib-reduce-user_access_begin-boundaries-in-strncpy_from_user-and-strnlen_user
+++ a/lib/strnlen_user.c
@@ -27,13 +27,6 @@ static inline long do_strnlen_user(const
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..
*/
@@ -109,6 +102,13 @@ long strnlen_user(const char __user *str
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();
_
Patches currently in -mm which might be from christophe.leroy@xxxxxx are
lib-reduce-user_access_begin-boundaries-in-strncpy_from_user-and-strnlen_user.patch
init-fix-misleading-this-architecture-does-not-have-kernel-memory-protection-message.patch
