From: Kees Cook <keescook@chromium.org>
To: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
linux-hyperv@vger.kernel.org,
Nathan Chancellor <nathan@kernel.org>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: [PATCH] Drivers: hv: vmbus: Split memcpy of flex-array
Date: Fri, 23 Sep 2022 20:07:41 -0700 [thread overview]
Message-ID: <20220924030741.3345349-1-keescook@chromium.org> (raw)
To work around a misbehavior of the compiler's ability to see into
composite flexible array structs (as detailed in the coming memcpy()
hardening series[1]), split the memcpy() of the header and the payload
so no false positive run-time overflow warning will be generated. As it
turns out, this appears to actually reduce the text size:
$ size drivers/hv/vmbus_drv.o.before drivers/hv/vmbus_drv.o
text data bss dec hex filename
22968 5239 232 28439 6f17 drivers/hv/vmbus_drv.o.before
23032 5239 232 28503 6f57 drivers/hv/vmbus_drv.o
[1] https://lore.kernel.org/linux-hardening/20220901065914.1417829-2-keescook@chromium.org/
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: linux-hyperv@vger.kernel.org
Reported-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/hv/vmbus_drv.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 23c680d1a0f5..9b111a8262e3 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1131,7 +1131,8 @@ void vmbus_on_msg_dpc(unsigned long data)
return;
INIT_WORK(&ctx->work, vmbus_onmessage_work);
- memcpy(&ctx->msg, &msg_copy, sizeof(msg->header) + payload_size);
+ ctx->msg.header = msg_copy.header;
+ memcpy(&ctx->msg.payload, msg_copy.u.payload, payload_size);
/*
* The host can generate a rescind message while we
--
2.34.1
next reply other threads:[~2022-09-24 3:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-24 3:07 Kees Cook [this message]
2022-09-24 3:42 ` [PATCH] Drivers: hv: vmbus: Split memcpy of flex-array Gustavo A. R. Silva
2022-09-24 4:22 ` Kees Cook
2022-09-24 10:34 ` Wei Liu
2022-09-27 21:23 ` Kees Cook
2022-09-27 20:46 ` Nathan Chancellor
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