在 2021/6/24 11:24, Matthew Wilcox 写道:

On Thu, Jun 24, 2021 at 11:10:41AM +0800, Chen Huang wrote:

quoted

In userspace, I perform such operation:

 	fd = open("/tmp/test", O_RDWR | O_SYNC);
        access_address = (char *)mmap(NULL, uio_size, PROT_READ, MAP_SHARED, uio_fd, 0);
        ret = write(fd, access_address + 2, sizeof(long));

... you know that accessing this at unaligned offsets isn't going to
work.  It's completely meaningless.  Why are you trying to do it?
.

Yeah, it's a wrong usage of access. But maybe it's still a problem
an userspace operation  makes the kernel crash.