[v1] misc: Remove variable-length arrays on the stack

[PATCH 05/23] io/channel-websock: Replace strlen(const_str) by sizeof(const_str) - 1

Posted by Philippe Mathieu-Daudé 4 years, 7 months ago

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>
---
 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 03c1f7cb62f..cd7bba6bde7 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"
-- 
2.26.3

Re: [PATCH 05/23] io/channel-websock: Replace strlen(const_str) by sizeof(const_str) - 1

Posted by Daniel P. Berrangé 4 years, 7 months ago

On Wed, May 05, 2021 at 11:10:29PM +0200, Philippe Mathieu-Daudé wrote:
> 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>
> ---
>  io/channel-websock.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


Regards,
Daniel
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