* [PATCH v2] Drivers: hv: vmbus: Split memcpy of flex-array
@ 2022-09-27 21:17 Kees Cook
2022-09-27 21:26 ` Gustavo A. R. Silva
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Kees Cook @ 2022-09-27 21:17 UTC (permalink / raw)
To: K. Y. Srinivasan
Cc: Kees Cook, Haiyang Zhang, Stephen Hemminger, Wei Liu, Dexuan Cui,
linux-hyperv, Nathan Chancellor, Gustavo A. R. Silva,
linux-kernel, linux-hardening
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. This
results in the already inlined memcpy getting unrolled a little more,
which very slightly increases 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
Avoids the run-time false-positive warning:
memcpy: detected field-spanning write (size 212) of single field "&ctx->msg" at drivers/hv/vmbus_drv.c:1133 (size 16)
[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>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
v2: - fix commit log, add tags and exact warning test from Nathan
v1: https://lore.kernel.org/lkml/20220924030741.3345349-1-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
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH v2] Drivers: hv: vmbus: Split memcpy of flex-array
2022-09-27 21:17 [PATCH v2] Drivers: hv: vmbus: Split memcpy of flex-array Kees Cook
@ 2022-09-27 21:26 ` Gustavo A. R. Silva
2022-09-27 21:26 ` Michael Kelley (LINUX)
2022-09-28 13:36 ` Wei Liu
2 siblings, 0 replies; 4+ messages in thread
From: Gustavo A. R. Silva @ 2022-09-27 21:26 UTC (permalink / raw)
To: Kees Cook
Cc: K. Y. Srinivasan, Haiyang Zhang, Stephen Hemminger, Wei Liu,
Dexuan Cui, linux-hyperv, Nathan Chancellor, linux-kernel,
linux-hardening
On Tue, Sep 27, 2022 at 02:17:36PM -0700, Kees Cook wrote:
> 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. This
> results in the already inlined memcpy getting unrolled a little more,
> which very slightly increases 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
>
> Avoids the run-time false-positive warning:
>
> memcpy: detected field-spanning write (size 212) of single field "&ctx->msg" at drivers/hv/vmbus_drv.c:1133 (size 16)
>
> [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>
> Tested-by: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Thanks!
--
Gustavo
> ---
> v2: - fix commit log, add tags and exact warning test from Nathan
> v1: https://lore.kernel.org/lkml/20220924030741.3345349-1-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
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* RE: [PATCH v2] Drivers: hv: vmbus: Split memcpy of flex-array
2022-09-27 21:17 [PATCH v2] Drivers: hv: vmbus: Split memcpy of flex-array Kees Cook
2022-09-27 21:26 ` Gustavo A. R. Silva
@ 2022-09-27 21:26 ` Michael Kelley (LINUX)
2022-09-28 13:36 ` Wei Liu
2 siblings, 0 replies; 4+ messages in thread
From: Michael Kelley (LINUX) @ 2022-09-27 21:26 UTC (permalink / raw)
To: Kees Cook, KY Srinivasan
Cc: Haiyang Zhang, Stephen Hemminger, Wei Liu, Dexuan Cui,
linux-hyperv@vger.kernel.org, Nathan Chancellor,
Gustavo A. R. Silva, linux-kernel@vger.kernel.org,
linux-hardening@vger.kernel.org
From: Kees Cook <keescook@chromium.org> Sent: Tuesday, September 27, 2022 2:18 PM
>
> 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. This
> results in the already inlined memcpy getting unrolled a little more,
> which very slightly increases 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
>
> Avoids the run-time false-positive warning:
>
> memcpy: detected field-spanning write (size 212) of single field "&ctx->msg" at
> drivers/hv/vmbus_drv.c:1133 (size 16)
>
> [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>
> Tested-by: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> v2: - fix commit log, add tags and exact warning test from Nathan
> v1: https://lore.kernel.org/lkml/20220924030741.3345349-1-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
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] Drivers: hv: vmbus: Split memcpy of flex-array
2022-09-27 21:17 [PATCH v2] Drivers: hv: vmbus: Split memcpy of flex-array Kees Cook
2022-09-27 21:26 ` Gustavo A. R. Silva
2022-09-27 21:26 ` Michael Kelley (LINUX)
@ 2022-09-28 13:36 ` Wei Liu
2 siblings, 0 replies; 4+ messages in thread
From: Wei Liu @ 2022-09-28 13:36 UTC (permalink / raw)
To: Kees Cook
Cc: K. Y. Srinivasan, Haiyang Zhang, Stephen Hemminger, Wei Liu,
Dexuan Cui, linux-hyperv, Nathan Chancellor, Gustavo A. R. Silva,
linux-kernel, linux-hardening
On Tue, Sep 27, 2022 at 02:17:36PM -0700, Kees Cook wrote:
> 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. This
> results in the already inlined memcpy getting unrolled a little more,
> which very slightly increases 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
>
> Avoids the run-time false-positive warning:
>
> memcpy: detected field-spanning write (size 212) of single field "&ctx->msg" at drivers/hv/vmbus_drv.c:1133 (size 16)
>
> [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>
> Tested-by: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: Kees Cook <keescook@chromium.org>
Applied to hyperv-next. Thanks.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-09-27 21:26 ` Gustavo A. R. Silva
2022-09-27 21:26 ` Michael Kelley (LINUX)
2022-09-28 13:36 ` Wei Liu
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