This is a note to let you know that I've just added the patch titled
lib/strscpy: Shut up KASAN false-positives in strscpy()
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
lib-strscpy-shut-up-kasan-false-positives-in-strscpy.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu Oct 22 03:56:50 PM CEST 2020
From: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Date: Thu, 1 Feb 2018 21:00:50 +0300
Subject: lib/strscpy: Shut up KASAN false-positives in strscpy()
From: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
commit 1a3241ff10d038ecd096d03380327f2a0b5840a6 upstream.
strscpy() performs the word-at-a-time optimistic reads. So it may may
access the memory past the end of the object, which is perfectly fine
since strscpy() doesn't use that (past-the-end) data and makes sure the
optimistic read won't cross a page boundary.
Use new read_word_at_a_time() to shut up the KASAN.
Note that this potentially could hide some bugs. In example bellow,
stscpy() will copy more than we should (1-3 extra uninitialized bytes):
char dst[8];
char *src;
src = kmalloc(5, GFP_KERNEL);
memset(src, 0xff, 5);
strscpy(dst, src, 8);
Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
lib/string.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/lib/string.c
+++ b/lib/string.c
@@ -202,7 +202,7 @@ ssize_t strscpy(char *dest, const char *
while (max >= sizeof(unsigned long)) {
unsigned long c, data;
- c = *(unsigned long *)(src+res);
+ c = read_word_at_a_time(src+res);
if (has_zero(c, &data, &constants)) {
data = prep_zero_mask(c, data, &constants);
data = create_zero_mask(data);
Patches currently in stable-queue which might be from aryabinin@xxxxxxxxxxxxx are
queue-4.4/x86-mm-ptdump-fix-soft-lockup-in-page-table-walker.patch
queue-4.4/mm-kasan-add-api-to-check-memory-regions.patch
queue-4.4/compiler.h-add-read_word_at_a_time-function.patch
queue-4.4/compiler.h-kasan-avoid-duplicating-__read_once_size_nocheck.patch
queue-4.4/mm-kasan-print-name-of-mem-caller-in-report.patch
queue-4.4/lib-strscpy-shut-up-kasan-false-positives-in-strscpy.patch
