On Fri, Sep 02, 2016 at 02:25:45PM +0200, Jiri Olsa wrote: > One of the bullets for hardened usercopy feature is: > - object must not overlap with kernel text > > which is what we expose via /proc/kcore. We can hit > this check and crash the system very easily just by > reading the text area in kcore file: > > usercopy: kernel memory exposure attempt detected from ffffffff8179a01f > (<kernel text>) (4065 bytes) > kernel BUG at mm/usercopy.c:75! > > Omitting kernel text area from kcore when there's > hardened usercopy feature is enabled.
That will completely break PT decoding, which relies on looking at the kernel text in /proc/kcore. Need a different fix here, perhaps some special copy function that is not hardened. -Andi
