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Date: Mon, 6 Mar 2017 11:09:46 -0800
From: Kees Cook <keescook@...omium.org>
To: kernel-hardening@...ts.openwall.com
Cc: Kees Cook <keescook@...omium.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Rik van Riel <riel@...hat.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Jakub Kicinski <jakub.kicinski@...ronome.com>,
Viresh Kumar <viresh.kumar@...aro.org>,
Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Dmitry Vyukov <dvyukov@...gle.com>,
Olof Johansson <olof@...om.net>,
Peter Zijlstra <peterz@...radead.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
linux-kernel@...r.kernel.org
Subject: [PATCH 6/6] refcount: Check bad states with CHECK_DATA_CORRUPTION
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.
Signed-off-by: Kees Cook <keescook@...omium.org>
---
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 <linux/refcount.h>
#include <linux/bug.h>
+/*
+ * 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
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