Date: Fri, 27 Oct 2017 22:33:01 +0900 From: Sergey Senozhatsky <sergey.senozhatsky@...il.com> To: "Tobin C. Harding" <me@...in.cc> Cc: kernel-hardening@...ts.openwall.com, "Jason A. Donenfeld" <Jason@...c4.com>, Theodore Ts'o <tytso@....edu>, Linus Torvalds <torvalds@...ux-foundation.org>, Kees Cook <keescook@...omium.org>, Paolo Bonzini <pbonzini@...hat.com>, Tycho Andersen <tycho@...ker.com>, "Roberts, William C" <william.c.roberts@...el.com>, Tejun Heo <tj@...nel.org>, Jordan Glover <Golden_Miller83@...tonmail.ch>, Greg KH <gregkh@...uxfoundation.org>, Petr Mladek <pmladek@...e.com>, Joe Perches <joe@...ches.com>, Ian Campbell <ijc@...lion.org.uk>, Sergey Senozhatsky <sergey.senozhatsky@...il.com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <wilal.deacon@....com>, Steven Rostedt <rostedt@...dmis.org>, Chris Fries <cfries@...gle.com>, Dave Weinstein <olorin@...gle.com>, Daniel Micay <danielmicay@...il.com>, Djalal Harouni <tixxdz@...il.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH V8 0/2] printk: hash addresses printed with %p On (10/26/17 13:53), Tobin C. Harding wrote: > Currently there are many places in the kernel where addresses are being > printed using an unadorned %p. Kernel pointers should be printed using > %pK allowing some control via the kptr_restrict sysctl. Exposing > addresses gives attackers sensitive information about the kernel layout > in memory. > > We can reduce the attack surface by hashing all addresses printed with > %p. This will of course break some users, forcing code printing needed > addresses to be updated. > > With this version we include hashing of malformed specifiers also. > Malformed specifiers include incomplete (e.g %pi) and also non-existent > specifiers. checkpatch should warn for non-existent specifiers but > AFAICT won't warn for incomplete specifiers. > > Here is the behaviour that this set implements. > > For kpt_restrict==0 > > Randomness not ready: > printed with %p: (pointer) # NOTE: with padding > Valid pointer: > printed with %pK: deadbeefdeadbeef > printed with %p: 0xdeadbeef > malformed specifier (eg %i): 0xdeadbeef > NULL pointer: > printed with %pK: 0000000000000000 > printed with %p: (null) # NOTE: no padding > malformed specifier (eg %i): (null) a quick question: do we care about cases when kernel pointers are printed with %x/%X and not with %p? -ss
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.