linux-kernel - Re: [PATCH] kernfs: fix potential NULL dereference in mmap handler

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Message-ID: <2025040117-flock-narrow-3b19@gregkh>
Date: Tue, 1 Apr 2025 16:51:13 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Wentao Liang <vulab@...as.ac.cn>
Cc: tj@...nel.org, linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] kernfs: fix potential NULL dereference in mmap handler

On Tue, Apr 01, 2025 at 11:18:59PM +0800, Wentao Liang wrote:
> The kernfs_fop_mmap() invokes the '->mmap' callback without verifying its
> existence. This leads to a NULL pointer dereference when the kernfs node
> does not define the operation, resulting in an invalid memory access.

How can that happen with any in-kernel user of kernfs?  If you try to
mmap any sysfs file today does this trigger?

thanks,

greg k-h