Re: passing __user function parameter from kernel_module result in EFAULT

On Tue, Apr 21, 2020 at 09:14:00PM +0300, Lev R. Oshvang . wrote:

Hi all, I am trying to do a mount from kernel module in kernel 5.4 on x86_64. It fails with -14, I tried to set_fs(USER_DS) before calling do_mount but it did not help.

do_mount() returns -EFAUTL when it checks filename validity just at the very first lines of do_mount ().

Are there other tricks to do in order to overcome and access_ok checks?

No "trick" is needed, just properly convert the data to a kernel pointer and you should be fine. Never touch the data pointed to by a userspace pointer. greg k-h