linux-kernel - [PATCH 4/5] kmsan: enter the runtime around kmsan_internal_memmove

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Message-ID: <20250507160012.3311104-4-glider@google.com>
Date: Wed,  7 May 2025 18:00:11 +0200
From: Alexander Potapenko <glider@...gle.com>
To: glider@...gle.com
Cc: elver@...gle.com, dvyukov@...gle.com, bvanassche@....org, 
	kent.overstreet@...ux.dev, iii@...ux.ibm.com, akpm@...ux-foundation.org, 
	linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com
Subject: [PATCH 4/5] kmsan: enter the runtime around kmsan_internal_memmove_metadata()
 call

kmsan_internal_memmove_metadata() transitively calls stack_depot_save()
(via kmsan_internal_chain_origin() and kmsan_save_stack_with_flags()),
which may allocate memory. Guard it with kmsan_enter_runtime() and
kmsan_leave_runtime() to avoid recursion.

This bug was spotted by CONFIG_WARN_CAPABILITY_ANALYSIS=y

Cc: Marco Elver <elver@...gle.com>
Cc: Bart Van Assche <bvanassche@....org>
Cc: Kent Overstreet <kent.overstreet@...ux.dev>
Signed-off-by: Alexander Potapenko <glider@...gle.com>
---
 mm/kmsan/hooks.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 05f2faa540545..97de3d6194f07 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -275,8 +275,10 @@ void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,
 		 * Don't check anything, just copy the shadow of the copied
 		 * bytes.
 		 */
+		kmsan_enter_runtime();
 		kmsan_internal_memmove_metadata((void *)to, (void *)from,
 						to_copy - left);
+		kmsan_leave_runtime();
 	}
 	user_access_restore(ua_flags);
 }
-- 
2.49.0.967.g6a0df3ecc3-goog