Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936239AbdCVTa6 (ORCPT ); Wed, 22 Mar 2017 15:30:58 -0400 Received: from mail-io0-f169.google.com ([209.85.223.169]:32882 "EHLO mail-io0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935017AbdCVTam (ORCPT ); Wed, 22 Mar 2017 15:30:42 -0400 MIME-Version: 1.0 In-Reply-To: <1488827386-87193-7-git-send-email-keescook@chromium.org> References: <1488827386-87193-1-git-send-email-keescook@chromium.org> <1488827386-87193-7-git-send-email-keescook@chromium.org> From: Kees Cook Date: Wed, 22 Mar 2017 12:30:39 -0700 X-Google-Sender-Auth: HvXvK8CJldsUO_SJ3HBj0z-j3s8 Message-ID: Subject: Re: [PATCH 6/6] refcount: Check bad states with CHECK_DATA_CORRUPTION To: Peter Zijlstra Cc: Kees Cook , Andrew Morton , Rik van Riel , "Paul E. McKenney" , Jakub Kicinski , Viresh Kumar , Ingo Molnar , Thomas Gleixner , Dmitry Vyukov , Olof Johansson , Josh Poimboeuf , LKML , "kernel-hardening@lists.openwall.com" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4467 Lines: 127 On Mon, Mar 6, 2017 at 11:09 AM, Kees Cook wrote: > This converts from WARN() to CHECK_DATA_CORRUPTION() (so that system > builders can choose between WARN and BUG). Additionally moves refcount_t > sanity-check conditionals into regular function flow. > > Now when built with CONFIG_BUG_ON_DATA_CORRUPTION, the LKDTM REFCOUNT_* > tests correctly kill offending processes. Any feedback on this change? I'd like to get this and the prior patches into -next soon for more testing. -Kees > > Signed-off-by: Kees Cook > --- > lib/refcount.c | 33 +++++++++++++++++++++------------ > 1 file changed, 21 insertions(+), 12 deletions(-) > > diff --git a/lib/refcount.c b/lib/refcount.c > index 1d33366189d1..54aff1e0582f 100644 > --- a/lib/refcount.c > +++ b/lib/refcount.c > @@ -37,6 +37,13 @@ > #include > #include > > +/* > + * CHECK_DATA_CORRUPTION() is defined with __must_check, but we have a > + * couple places where we want to report a condition that has already > + * been checked, so this lets us cheat __must_check. > + */ > +#define REFCOUNT_CHECK(cond, str) unlikely(CHECK_DATA_CORRUPTION(cond, str)) > + > bool refcount_add_not_zero(unsigned int i, refcount_t *r) > { > unsigned int old, new, val = atomic_read(&r->refs); > @@ -58,7 +65,8 @@ bool refcount_add_not_zero(unsigned int i, refcount_t *r) > val = old; > } > > - WARN(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n"); > + REFCOUNT_CHECK(new == UINT_MAX, > + "refcount_t: add saturated; leaking memory.\n"); > > return true; > } > @@ -66,7 +74,8 @@ EXPORT_SYMBOL_GPL(refcount_add_not_zero); > > void refcount_add(unsigned int i, refcount_t *r) > { > - WARN(!refcount_add_not_zero(i, r), "refcount_t: addition on 0; use-after-free.\n"); > + REFCOUNT_CHECK(!refcount_add_not_zero(i, r), > + "refcount_t: addition on 0; use-after-free.\n"); > } > EXPORT_SYMBOL_GPL(refcount_add); > > @@ -97,7 +106,8 @@ bool refcount_inc_not_zero(refcount_t *r) > val = old; > } > > - WARN(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n"); > + REFCOUNT_CHECK(new == UINT_MAX, > + "refcount_t: inc saturated; leaking memory.\n"); > > return true; > } > @@ -111,7 +121,8 @@ EXPORT_SYMBOL_GPL(refcount_inc_not_zero); > */ > void refcount_inc(refcount_t *r) > { > - WARN(!refcount_inc_not_zero(r), "refcount_t: increment on 0; use-after-free.\n"); > + REFCOUNT_CHECK(!refcount_inc_not_zero(r), > + "refcount_t: increment on 0; use-after-free.\n"); > } > EXPORT_SYMBOL_GPL(refcount_inc); > > @@ -124,10 +135,9 @@ bool refcount_sub_and_test(unsigned int i, refcount_t *r) > return false; > > new = val - i; > - if (new > val) { > - WARN(new > val, "refcount_t: underflow; use-after-free.\n"); > + if (REFCOUNT_CHECK(new > val, > + "refcount_t: sub underflow; use-after-free.\n")) > return false; > - } > > old = atomic_cmpxchg_release(&r->refs, val, new); > if (old == val) > @@ -164,7 +174,8 @@ EXPORT_SYMBOL_GPL(refcount_dec_and_test); > > void refcount_dec(refcount_t *r) > { > - WARN(refcount_dec_and_test(r), "refcount_t: decrement hit 0; leaking memory.\n"); > + REFCOUNT_CHECK(refcount_dec_and_test(r), > + "refcount_t: decrement hit 0; leaking memory.\n"); > } > EXPORT_SYMBOL_GPL(refcount_dec); > > @@ -203,10 +214,9 @@ bool refcount_dec_not_one(refcount_t *r) > return false; > > new = val - 1; > - if (new > val) { > - WARN(new > val, "refcount_t: underflow; use-after-free.\n"); > + if (REFCOUNT_CHECK(new > val, > + "refcount_t: dec underflow; use-after-free.\n")) > return true; > - } > > old = atomic_cmpxchg_release(&r->refs, val, new); > if (old == val) > @@ -264,4 +274,3 @@ bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock) > return true; > } > EXPORT_SYMBOL_GPL(refcount_dec_and_lock); > - > -- > 2.7.4 > -- Kees Cook Pixel Security