linux-kernel - Re: [PATCH] HID: i2c-hid: fix potential buffer overflow in i2c_hid_get

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Message-ID: <aV5_76eRrcGJ1ehE@anonymous>
Date: Thu, 8 Jan 2026 00:08:22 +0800
From: kenkinming2002@...il.com
To: Benjamin Tissoires <bentiss@...nel.org>
Cc: jikos@...nel.org, linux-input@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HID: i2c-hid: fix potential buffer overflow in
 i2c_hid_get_report()

On Wed, Jan 07, 2026 at 03:20:13PM +0100, Benjamin Tissoires wrote:
> It makes sense to put this min call here, but it's already present at
> line 304 a few lines after. Could you remove that second check (and
> unnecessary one after your change).

The min call at line 304 uses ret_count which comes from the first 2
bytes in the device response and indicates the actual size of the
returned report descriptor. Notice that importantly ret_count can be
strictly smaller than ihid->bufsize because persumably not all reports
have the same size. The behavior will change if the caller provides a
larger buffer than is necessary. With the min call at line 304, we will
return the actual size of the report descriptor (without the 2 bytes
length header). Without the min call at 304, we will instead return the
size of supplied buffer.

Yours sincerely,
Ken Kwok