linux-kernel - Re: [PATCH] staging: speakup: fix wraparound in uaccess length check

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Date:   Sat, 7 Jul 2018 10:13:47 +0200
From:   Samuel Thibault <samuel.thibault@...-lyon.org>
To:     Jann Horn <jannh@...gle.com>
Cc:     William Hubbs <w.d.hubbs@...il.com>,
        Chris Brannon <chris@...-brannons.com>,
        Kirk Reiser <kirk@...sers.ca>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, speakup@...ux-speakup.org,
        devel@...verdev.osuosl.org
Subject: Re: [PATCH] staging: speakup: fix wraparound in uaccess length check

Jann Horn, le sam. 07 juil. 2018 03:53:44 +0200, a ecrit:
> @@ -257,6 +257,8 @@ static ssize_t softsynthx_read(struct file *fp, char __user *buf, size_t count,
>  				0x80 | (ch & 0x3f)
>  			};
>  
> +			if (chars_sent + 2 > count)
> +				break;
>  			if (copy_to_user(cp, s, sizeof(s)))
>  				return -EFAULT;

Err, but then we have lost 'ch' that was consumed by the
synth_buffer_getc() call, so the fix seems wrong to me.

Nacked-by: Samuel Thibault <samuel.thibault@...-lyon.org>

Samuel