On Thu, Mar 30, 2017 at 09:45:26AM -0700, Kees Cook wrote: > On Wed, Mar 29, 2017 at 11:44 PM, Tommi Rantala > <tommi.t.rantala@xxxxxxxxx> wrote: > > Hi, > > > > Running: > > > > $ sudo x86info -a > > > > On this HP ZBook 15 G3 laptop kills the x86info process with segfault and > > produces the following kernel BUG. > > > > $ git describe > > v4.11-rc4-40-gfe82203 > > > > It is also reproducible with the fedora kernel: 4.9.14-200.fc25.x86_64 > > > > Full dmesg output here: https://pastebin.com/raw/Kur2mpZq > > > > [ 51.418954] usercopy: kernel memory exposure attempt detected from > > ffff880000090000 (dma-kmalloc-256) (4096 bytes) > > This seems like a real exposure: the copy is attempting to read 4096 > bytes from a 256 byte object. The code[1] is doing a 4k read from /dev/mem in the range 0x90000 -> 0xa0000 According to arch/x86/mm/init.c:devmem_is_allowed, that's still valid.. Note that the printk is using the direct mapping address. Is that what's being passed down to devmem_is_allowed now ? If so, that's probably what broke. Dave [1] https://github.com/kernelslacker/x86info/blob/master/mptable.c -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
