linux-kernel - Re: [PATCH] usb: gadget: prevent a ternary sign expansion bug

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

Dan Carpenter <dan.carpenter@...cle.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@...cle.com>

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

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

-- 
balbi

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