linux-kernel - [PATCH v2 06/33] kmsan: Fix kmsan_copy_to_user() on arches with overlapping address spaces

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Message-ID: <20231121220155.1217090-7-iii@linux.ibm.com>
Date:   Tue, 21 Nov 2023 23:01:00 +0100
From:   Ilya Leoshkevich <iii@...ux.ibm.com>
To:     Alexander Gordeev <agordeev@...ux.ibm.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Marco Elver <elver@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Pekka Enberg <penberg@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>
Cc:     Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-s390@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Ilya Leoshkevich <iii@...ux.ibm.com>
Subject: [PATCH v2 06/33] kmsan: Fix kmsan_copy_to_user() on arches with overlapping address spaces

Comparing pointers with TASK_SIZE does not make sense when kernel and
userspace overlap. Assume that we are handling user memory access in
this case.

Reported-by: Alexander Gordeev <agordeev@...ux.ibm.com>
Reviewed-by: Alexander Potapenko <glider@...gle.com>
Signed-off-by: Ilya Leoshkevich <iii@...ux.ibm.com>
---
 mm/kmsan/hooks.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 5d6e2dee5692..eafc45f937eb 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -267,7 +267,8 @@ void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
 		return;
 
 	ua_flags = user_access_save();
-	if ((u64)to < TASK_SIZE) {
+	if (!IS_ENABLED(CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE) ||
+	    (u64)to < TASK_SIZE) {
 		/* This is a user memory access, check it. */
 		kmsan_internal_check_memory((void *)from, to_copy - left, to,
 					    REASON_COPY_TO_USER);
-- 
2.41.0