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Date: Thu, 5 Jan 2023 12:18:18 +0000
From: Lee Jones <lee@kernel.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org, patches@lists.linux.dev,
	Andrzej Pietrasiewicz <andrzej.p@collabora.com>,
	John Keeping <john@metanate.com>, Sasha Levin <sashal@kernel.org>
Subject: Re: [PATCH 5.15 481/731] usb: gadget: f_hid: fix f_hidg lifetime vs
 cdev
Message-ID: <Y7bACmZQdEhlf121@google.com>
References: <20221228144256.536395940@linuxfoundation.org>
 <20221228144310.493605271@linuxfoundation.org>
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In-Reply-To: <20221228144310.493605271@linuxfoundation.org>

On Wed, 28 Dec 2022, Greg Kroah-Hartman wrote:

> From: John Keeping <john@metanate.com>
> 
> [ Upstream commit 89ff3dfac604614287ad5aad9370c3f984ea3f4b ]
> 
> The embedded struct cdev does not have its lifetime correctly tied to
> the enclosing struct f_hidg, so there is a use-after-free if /dev/hidgN
> is held open while the gadget is deleted.
> 
> This can readily be replicated with libusbgx's example programs (for
> conciseness - operating directly via configfs is equivalent):
> 
> 	gadget-hid
> 	exec 3<> /dev/hidg0
> 	gadget-vid-pid-remove
> 	exec 3<&-
> 
> Pull the existing device up in to struct f_hidg and make use of the
> cdev_device_{add,del}() helpers.  This changes the lifetime of the
> device object to match struct f_hidg, but note that it is still added
> and deleted at the same time.
> 
> Fixes: 71adf1189469 ("USB: gadget: add HID gadget driver")
> Tested-by: Lee Jones <lee@kernel.org>
> Reviewed-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> Reviewed-by: Lee Jones <lee@kernel.org>
> Signed-off-by: John Keeping <john@metanate.com>
> Link: https://lore.kernel.org/r/20221122123523.3068034-2-john@metanate.com
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  drivers/usb/gadget/function/f_hid.c | 52 ++++++++++++++++-------------
>  1 file changed, 28 insertions(+), 24 deletions(-)
 
Dear Stable,

Would you be kind enough to take this back as far back as linux.4.14.y
please?  There is a trivial fix-up required for kernels older than
v5.15, but it's the same fix-up back through v4.14.

Thanks.

--- 
Lee Jones [李琼斯]