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From: Jens Axboe <[email protected]>
To: Ammar Faizi <[email protected]>
Cc: GNU/Weeb Mailing List <[email protected]>,
	io-uring Mailing list <[email protected]>,
	Tea Inside Mailing List <[email protected]>,
	Linux Kernel Mailing List <[email protected]>,
	Alviro Iskandar Setiawan <[email protected]>,
	kernel test robot <[email protected]>,
	Dan Carpenter <[email protected]>,
	"Chen, Rong A" <[email protected]>,
	Pavel Begunkov <[email protected]>
Subject: Re: [PATCH io_uring-5.17] io_uring: Fix build error potential reading uninitialized value
Date: Mon, 7 Feb 2022 06:45:57 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 2/7/22 4:43 AM, Ammar Faizi wrote:
> From: Alviro Iskandar Setiawan <[email protected]>
> 
> In io_recv() if import_single_range() fails, the @flags variable is
> uninitialized, then it will goto out_free.
> 
> After the goto, the compiler doesn't know that (ret < min_ret) is
> always true, so it thinks the "if ((flags & MSG_WAITALL) ..."  path
> could be taken.
> 
> The complaint comes from gcc-9 (Debian 9.3.0-22) 9.3.0:
> ```
>   fs/io_uring.c:5238 io_recvfrom() error: uninitialized symbol 'flags'
> ```
> Fix this by bypassing the @ret and @flags check when
> import_single_range() fails.

The compiler should be able to deduce this, and I guess newer compilers
do which is why we haven't seen this warning before. I'm fine with doing
this as a cleanup, but I think the commit title should be modified a
bit. It sounds like there might be an issue reading uninitialized data,
which isn't actually true.

-- 
Jens Axboe


  reply	other threads:[~2022-02-07 13:46 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <61f5a2fa./zZ+BkSwdkmvxv7x%[email protected]>
2022-01-30  9:11 ` [ammarfaizi2-block:testing/io_uring-sendto-recvfrom.v1] BUILD SUCCESS 68d110c39241b887ec388cd3316dbedb85b0cbcf Ammar Faizi
2022-02-07  6:13   ` Chen, Rong A
2022-02-07 11:43     ` [PATCH io_uring-5.17] io_uring: Fix build error potential reading uninitialized value Ammar Faizi
2022-02-07 13:45       ` Jens Axboe [this message]
2022-02-07 14:05         ` [PATCH io_uring-5.17 v2] io_uring: Clean up a false-positive warning from GCC 9.3.0 Ammar Faizi
2022-02-07 15:38           ` Jens Axboe
2022-02-07 14:20         ` [PATCH io_uring-5.17] io_uring: Fix build error potential reading uninitialized value Dan Carpenter
2022-02-07 14:33           ` Alviro Iskandar Setiawan
2022-02-07 15:37             ` Jens Axboe

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