* [PATCH] hw/xen: Check if len is 0 before memcpy()
@ 2025-01-08 11:31 Akihiko Odaki
2025-01-08 11:42 ` Philippe Mathieu-Daudé
2025-01-08 11:47 ` David Woodhouse
0 siblings, 2 replies; 3+ messages in thread
From: Akihiko Odaki @ 2025-01-08 11:31 UTC (permalink / raw)
To: David Woodhouse, Paul Durrant, Michael S. Tsirkin,
Marcel Apfelbaum, Paolo Bonzini, Richard Henderson,
Eduardo Habkost
Cc: qemu-devel, devel, Akihiko Odaki
data->data can be NULL when len is 0. Strictly speaking, the behavior
of memcpy() in such a scenario is undefined so UBSan complaints.
Satisfy UBSan by checking if len is 0 before memcpy().
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
hw/i386/kvm/xen_xenstore.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/hw/i386/kvm/xen_xenstore.c b/hw/i386/kvm/xen_xenstore.c
index 59691056670e..17802aa33d20 100644
--- a/hw/i386/kvm/xen_xenstore.c
+++ b/hw/i386/kvm/xen_xenstore.c
@@ -532,6 +532,10 @@ static void xs_read(XenXenstoreState *s, unsigned int req_id,
return;
}
+ if (!len) {
+ return;
+ }
+
memcpy(&rsp_data[rsp->len], data->data, len);
rsp->len += len;
}
---
base-commit: 38d0939b86e2eef6f6a622c6f1f7befda0146595
change-id: 20241227-xen-fb5a15cc0ca7
Best regards,
--
Akihiko Odaki <akihiko.odaki@daynix.com>
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] hw/xen: Check if len is 0 before memcpy()
2025-01-08 11:31 [PATCH] hw/xen: Check if len is 0 before memcpy() Akihiko Odaki
@ 2025-01-08 11:42 ` Philippe Mathieu-Daudé
2025-01-08 11:47 ` David Woodhouse
1 sibling, 0 replies; 3+ messages in thread
From: Philippe Mathieu-Daudé @ 2025-01-08 11:42 UTC (permalink / raw)
To: Akihiko Odaki, David Woodhouse, Paul Durrant, Michael S. Tsirkin,
Marcel Apfelbaum, Paolo Bonzini, Richard Henderson,
Eduardo Habkost
Cc: qemu-devel, devel
On 8/1/25 12:31, Akihiko Odaki wrote:
> data->data can be NULL when len is 0. Strictly speaking, the behavior
> of memcpy() in such a scenario is undefined so UBSan complaints.
>
> Satisfy UBSan by checking if len is 0 before memcpy().
>
> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> ---
> hw/i386/kvm/xen_xenstore.c | 4 ++++
> 1 file changed, 4 insertions(+)
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] hw/xen: Check if len is 0 before memcpy()
2025-01-08 11:31 [PATCH] hw/xen: Check if len is 0 before memcpy() Akihiko Odaki
2025-01-08 11:42 ` Philippe Mathieu-Daudé
@ 2025-01-08 11:47 ` David Woodhouse
1 sibling, 0 replies; 3+ messages in thread
From: David Woodhouse @ 2025-01-08 11:47 UTC (permalink / raw)
To: Akihiko Odaki, Paul Durrant, Michael S. Tsirkin, Marcel Apfelbaum,
Paolo Bonzini, Richard Henderson, Eduardo Habkost
Cc: qemu-devel, devel
[-- Attachment #1: Type: text/plain, Size: 1094 bytes --]
On Wed, 2025-01-08 at 20:31 +0900, Akihiko Odaki wrote:
> data->data can be NULL when len is 0. Strictly speaking, the behavior
> of memcpy() in such a scenario is undefined so UBSan complaints.
>
> Satisfy UBSan by checking if len is 0 before memcpy().
>
> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Thanks.
> ---
> hw/i386/kvm/xen_xenstore.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/hw/i386/kvm/xen_xenstore.c b/hw/i386/kvm/xen_xenstore.c
> index 59691056670e..17802aa33d20 100644
> --- a/hw/i386/kvm/xen_xenstore.c
> +++ b/hw/i386/kvm/xen_xenstore.c
> @@ -532,6 +532,10 @@ static void xs_read(XenXenstoreState *s,
> unsigned int req_id,
> return;
> }
>
> + if (!len) {
> + return;
> + }
> +
> memcpy(&rsp_data[rsp->len], data->data, len);
> rsp->len += len;
> }
>
> ---
> base-commit: 38d0939b86e2eef6f6a622c6f1f7befda0146595
> change-id: 20241227-xen-fb5a15cc0ca7
>
> Best regards,
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2025-01-08 11:31 [PATCH] hw/xen: Check if len is 0 before memcpy() Akihiko Odaki
2025-01-08 11:42 ` Philippe Mathieu-Daudé
2025-01-08 11:47 ` David Woodhouse
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