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.

Add a check to ensure the '->mmap' callback is present before invocation. Return -EINVAL when uninitialized to prevent the invalid access.

I think that's already checked through KERNFS_HAS_MMAP.

Thanks.