On Mon, Mar 6, 2017 at 11:09 AM, Kees Cook <[email protected]> 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 <[email protected]> > --- > 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 > -- Kees Cook Pixel Security
