linux-kernel - Re: [PATCH] nvme: Ensure ret is always initialized in

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Date:   Fri, 6 May 2022 08:06:33 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Jens Axboe <axboe@...com>, Christoph Hellwig <hch@....de>,
        Keith Busch <kbusch@...nel.org>,
        Sagi Grimberg <sagi@...mberg.me>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, Kanchan Joshi <joshi.k@...sung.com>,
        Anuj Gupta <anuj20.g@...sung.com>,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] nvme: Ensure ret is always initialized in

Ugh, subject should be:

nvme: Ensure ret is always initialized in nvme_ns_head_chr_uring_cmd()

I can resend if this is the correct thing to do.

On Fri, May 06, 2022 at 08:03:58AM -0700, Nathan Chancellor wrote:
> Clang warns:
> 
>   drivers/nvme/host/ioctl.c:674:6: error: variable 'ret' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
>           if (ns)
>               ^~
>   drivers/nvme/host/ioctl.c:677:9: note: uninitialized use occurs here
>           return ret;
>                  ^~~
>   drivers/nvme/host/ioctl.c:674:2: note: remove the 'if' if its condition is always true
>           if (ns)
>           ^~~~~~~
>   drivers/nvme/host/ioctl.c:672:9: note: initialize the variable 'ret' to silence this warning
>           int ret;
>                  ^
>                   = 0
>   1 error generated.
> 
> Initialize ret to zero so that it cannot be used uninitialized.
> 
> Fixes: 271ee3df5cca ("nvme: wire-up uring-cmd support for io-passthru on char-device.")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1630
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
> 
> Or alternatively, remove the 'if (ns)' if ns can never be NULL; I tried
> going down the rabbit hole to see if that is possible but I got a little
> lost :^)
> 
>  drivers/nvme/host/ioctl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
> index 9db88f2c15f8..3ad5285c1f96 100644
> --- a/drivers/nvme/host/ioctl.c
> +++ b/drivers/nvme/host/ioctl.c
> @@ -669,7 +669,7 @@ int nvme_ns_head_chr_uring_cmd(struct io_uring_cmd *ioucmd,
>  	struct nvme_ns_head *head = container_of(cdev, struct nvme_ns_head, cdev);
>  	int srcu_idx = srcu_read_lock(&head->srcu);
>  	struct nvme_ns *ns = nvme_find_path(head);
> -	int ret;
> +	int ret = 0;
>  
>  	if (ns)
>  		ret = nvme_ns_uring_cmd(ns, ioucmd, issue_flags);
> 
> base-commit: 002b149a51a53facaf26d7c6f2c1fe718673683c
> -- 
> 2.36.0
>