linux-kernel - Re: [PATCH] io_uring/net: fix build warning for !CONFIG

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Message-ID: <275033e5-d3fe-400a-9e53-de1286adb107@gmail.com>
Date: Thu, 27 Feb 2025 13:49:25 +0000
From: Pavel Begunkov <asml.silence@...il.com>
To: Arnd Bergmann <arnd@...nel.org>, Jens Axboe <axboe@...nel.dk>
Cc: Arnd Bergmann <arnd@...db.de>, Gabriel Krisman Bertazi <krisman@...e.de>,
 David Wei <dw@...idwei.uk>, io-uring@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] io_uring/net: fix build warning for !CONFIG_COMPAT

On 2/27/25 13:20, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> A code rework resulted in an uninitialized return code when COMPAT
> mode is disabled:

As mentioned in the lkp report, it should be a false positive.

> 
> io_uring/net.c:722:6: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
>    722 |         if (io_is_compat(req->ctx)) {
>        |             ^~~~~~~~~~~~~~~~~~~~~~
> io_uring/net.c:736:15: note: uninitialized use occurs here
>    736 |         if (unlikely(ret))
>        |                      ^~~
> 
> Since io_is_compat() turns into a compile-time 'false', the #ifdef
> here is completely unnecessary, and removing it avoids the warning.

I don't think __get_compat_msghdr() and other helpers are
compiled for !COMPAT. I'd just silence it like:

if (io_is_compat(req->ctx)) {
	ret = -EFAULT;
#ifdef CONFIG_COMPAT
	...
#endif CONFIG_COMPAT
}
	
Let's see if Jens wants to fix it up in the tree.

-- 
Pavel Begunkov