This is a note to let you know that I've just added the patch titled
compiler.h: Add read_word_at_a_time() function.
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:
compiler.h-add-read_word_at_a_time-function.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 21:00:49 +0300
Subject: compiler.h: Add read_word_at_a_time() function.
From: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
commit 7f1e541fc8d57a143dd5df1d0a1276046e08c083 upstream.
Sometimes we know that it's safe to do potentially out-of-bounds access
because we know it won't cross a page boundary. Still, KASAN will
report this as a bug.
Add read_word_at_a_time() function which is supposed to be used in such
cases. In read_word_at_a_time() KASAN performs relaxed check - only the
first byte of access is validated.
Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 4.4: adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/compiler.h | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -292,6 +292,7 @@ static __always_inline void __write_once
* with an explicit memory barrier or atomic instruction that provides the
* required ordering.
*/
+#include <linux/kasan-checks.h>
#define __READ_ONCE(x, check) \
({ \
@@ -310,6 +311,13 @@ static __always_inline void __write_once
*/
#define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
+static __no_kasan_or_inline
+unsigned long read_word_at_a_time(const void *addr)
+{
+ kasan_check_read(addr, 1);
+ return *(unsigned long *)addr;
+}
+
#define WRITE_ONCE(x, val) \
({ \
union { typeof(x) __val; char __c[1]; } __u = \
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
