On 03/30/2017 10:37 AM, Kees Cook wrote: > On Thu, Mar 30, 2017 at 10:27 AM, Laura Abbott <[email protected]> wrote: >> 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? >> >> 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. > > Reads out of /dev/mem should be restricted to non-RAM on Fedora, yes? > > Tommi, do your kernels have CONFIG_STRICT_DEVMEM=y ? > > -Kees >
CONFIG_STRICT_DEVMEM should be on in all Fedora kernels. Thanks, Laura
