Messages in this thread | | | Date | Mon, 5 Sep 2016 09:27:39 -0700 | From | Andi Kleen <> | Subject | Re: [PATCH] fs/proc/kcore.c: Omit kernel text area for hardened usercopy feature |
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On Mon, Sep 05, 2016 at 10:47:22AM +0200, Jiri Olsa wrote: > On Fri, Sep 02, 2016 at 08:17:13AM -0700, Andi Kleen wrote: > > 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. > > how about something like this
Looks good to me, but you would need the *_nocheck variant for non x86 architectures too of course.
-Andi
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