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From:   Felipe Balbi <balbi@kernel.org>
To:     Dan Carpenter <dan.carpenter@oracle.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Alan Stern <stern@rowland.harvard.edu>,
        Jens Axboe <axboe@kernel.dk>,
        Felix Kuehling <Felix.Kuehling@amd.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Zhang Qilong <zhangqilong3@huawei.com>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] usb: gadget: prevent a ternary sign expansion bug
In-Reply-To: <YIE7RrBPLWc3XtMg@mwanda>
References: <YIE7RrBPLWc3XtMg@mwanda>
Date:   Thu, 22 Apr 2021 14:03:49 +0300
Message-ID: <87im4emvhm.fsf@kernel.org>
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Dan Carpenter <dan.carpenter@oracle.com> writes:

> The problem is that "req->actual" is a u32, "req->status" is an int, and
> iocb->ki_complete() takes a long.  We would expect that a negative error
> code in "req->status" would translate to a negative long value.
>
> But what actually happens is that because "req->actual" is a u32, the
> error codes is type promoted to a high positive value and then remains
> a positive value when it is cast to long.  (No sign expansion).
>
> We can fix this by casting "req->status" to long.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

I'm just going to assume your type promotion rank is correct :-)

Acked-by: Felipe Balbi <balbi@kernel.org>

=2D-=20
balbi

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