[v2] misc: Remove variable-length arrays on the stack

[PATCH v2 04/11] io/channel-websock: Replace strlen(const_str) by sizeof(const_str) - 1

Peter Maydell posted 11 patches 3 years, 5 months ago

Diff against v1
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Maintainers: Samuel Thibault <samuel.thibault@ens-lyon.org>, "Marc-André Lureau" <marcandre.lureau@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <richard.henderson@linaro.org>, Eduardo Habkost <eduardo@habkost.net>, "Michael S. Tsirkin" <mst@redhat.com>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Daniel Henrique Barboza <danielhb413@gmail.com>, "Cédric Le Goater" <clg@kaod.org>, David Gibson <david@gibson.dropbear.id.au>, Greg Kurz <groug@kaod.org>, Dmitry Fleytman <dmitry.fleytman@gmail.com>, Jason Wang <jasowang@redhat.com>, Gerd Hoffmann <kraxel@redhat.com>, "Daniel P. Berrangé" <berrange@redhat.com>

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[PATCH v2 04/11] io/channel-websock: Replace strlen(const_str) by sizeof(const_str) - 1

Posted by Peter Maydell 3 years, 5 months ago

From: Philippe Mathieu-Daudé <philmd@redhat.com>

The combined_key[... QIO_CHANNEL_WEBSOCK_GUID_LEN ...] array in
qio_channel_websock_handshake_send_res_ok() expands to a call
to strlen(QIO_CHANNEL_WEBSOCK_GUID), and the compiler doesn't
realize the string is const, so consider combined_key[] being
a variable-length array.

To remove the variable-length array, we provide it a hint to
the compiler by using sizeof() - 1 instead of strlen().

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 io/channel-websock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/io/channel-websock.c b/io/channel-websock.c
index 9619906ac36..fb4932ade70 100644
--- a/io/channel-websock.c
+++ b/io/channel-websock.c
@@ -32,7 +32,7 @@
 
 #define QIO_CHANNEL_WEBSOCK_CLIENT_KEY_LEN 24
 #define QIO_CHANNEL_WEBSOCK_GUID "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
-#define QIO_CHANNEL_WEBSOCK_GUID_LEN strlen(QIO_CHANNEL_WEBSOCK_GUID)
+#define QIO_CHANNEL_WEBSOCK_GUID_LEN (sizeof(QIO_CHANNEL_WEBSOCK_GUID) - 1)
 
 #define QIO_CHANNEL_WEBSOCK_HEADER_PROTOCOL "sec-websocket-protocol"
 #define QIO_CHANNEL_WEBSOCK_HEADER_VERSION "sec-websocket-version"
-- 
2.25.1

Re: [PATCH v2 04/11] io/channel-websock: Replace strlen(const_str) by sizeof(const_str) - 1

Posted by Richard Henderson 3 years, 3 months ago

On 8/20/22 01:39, Peter Maydell wrote:
> From: Philippe Mathieu-Daudé<philmd@redhat.com>
> 
> The combined_key[... QIO_CHANNEL_WEBSOCK_GUID_LEN ...] array in
> qio_channel_websock_handshake_send_res_ok() expands to a call
> to strlen(QIO_CHANNEL_WEBSOCK_GUID), and the compiler doesn't
> realize the string is const, so consider combined_key[] being
> a variable-length array.
> 
> To remove the variable-length array, we provide it a hint to
> the compiler by using sizeof() - 1 instead of strlen().
> 
> Signed-off-by: Philippe Mathieu-Daudé<philmd@redhat.com>
> Reviewed-by: Daniel P. Berrangé<berrange@redhat.com>
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
>   io/channel-websock.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~