On 03/30/2017 09:45 AM, Kees Cook wrote: > On Wed, Mar 29, 2017 at 11:44 PM, Tommi Rantala > <[email protected]> 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. > >> [...] >> [ 51.419063] Call Trace: >> [ 51.419066] read_mem+0x70/0x120 >> [ 51.419069] __vfs_read+0x28/0x130 >> [ 51.419072] ? security_file_permission+0x9b/0xb0 >> [ 51.419075] ? rw_verify_area+0x4e/0xb0 >> [ 51.419077] vfs_read+0x96/0x130 >> [ 51.419079] SyS_read+0x46/0xb0 >> [ 51.419082] ? SyS_lseek+0x87/0xb0 >> [ 51.419085] entry_SYSCALL_64_fastpath+0x1a/0xa9 > > I can't reproduce this myself, so I assume it's some specific /proc or > /sys file that I don't have. Are you able to get a strace of x86info > as it runs to see which file it is attempting to read here? > > Thanks! > > -Kees >
I can't see this on any of my Fedora systems. It looks like this is trying to read /dev/mem so I suspect your BIOS is putting out unexpected values. If you turn off hardened usercopy does x86info give you reasonable values? I'd also echo getting an strace. Thanks, Laura
