From 3429055f0451cd3a281f8ed6691335ead626b136 Mon Sep 17 00:00:00 2001 From: Alexander Potapenko Date: Wed, 20 Mar 2024 11:18:49 +0100 Subject: [PATCH] mm: kmsan: implement kmsan_memmove() Provide a hook that can be used by custom memcpy implementations to tell KMSAN that the metadata needs to be copied. Without that, false positive reports are possible in the cases where KMSAN fails to intercept memory initialization. Link: https://lore.kernel.org/all/3b7dbd88-0861-4638-b2d2-911c97a4cadf@I-love.SAKURA.ne.jp/ Link: https://lkml.kernel.org/r/20240320101851.2589698-1-glider@google.com Signed-off-by: Alexander Potapenko Suggested-by: Tetsuo Handa Reviewed-by: Marco Elver Cc: Dmitry Vyukov Cc: Linus Torvalds Cc: Tetsuo Handa Cc: Thomas Gleixner Signed-off-by: Andrew Morton --- include/linux/kmsan-checks.h | 15 +++++++++++++++ mm/kmsan/hooks.c | 11 +++++++++++ 2 files changed, 26 insertions(+) diff --git a/include/linux/kmsan-checks.h b/include/linux/kmsan-checks.h index c4cae333deec5..e1082dc40abc2 100644 --- a/include/linux/kmsan-checks.h +++ b/include/linux/kmsan-checks.h @@ -61,6 +61,17 @@ void kmsan_check_memory(const void *address, size_t size); void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy, size_t left); +/** + * kmsan_memmove() - Notify KMSAN about a data copy within kernel. + * @to: destination address in the kernel. + * @from: source address in the kernel. + * @size: number of bytes to copy. + * + * Invoked after non-instrumented version (e.g. implemented using assembly + * code) of memmove()/memcpy() is called, in order to copy KMSAN's metadata. + */ +void kmsan_memmove(void *to, const void *from, size_t to_copy); + #else static inline void kmsan_poison_memory(const void *address, size_t size, @@ -78,6 +89,10 @@ static inline void kmsan_copy_to_user(void __user *to, const void *from, { } +static inline void kmsan_memmove(void *to, const void *from, size_t to_copy) +{ +} + #endif #endif /* _LINUX_KMSAN_CHECKS_H */ diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c index 0b09daa188ef6..22e8657800eff 100644 --- a/mm/kmsan/hooks.c +++ b/mm/kmsan/hooks.c @@ -285,6 +285,17 @@ void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy, } EXPORT_SYMBOL(kmsan_copy_to_user); +void kmsan_memmove(void *to, const void *from, size_t size) +{ + if (!kmsan_enabled || kmsan_in_runtime()) + return; + + kmsan_enter_runtime(); + kmsan_internal_memmove_metadata(to, (void *)from, size); + kmsan_leave_runtime(); +} +EXPORT_SYMBOL(kmsan_memmove); + /* Helper function to check an URB. */ void kmsan_handle_urb(const struct urb *urb, bool is_out) { -- 2.30.2