Messages in this thread | | | From | Kees Cook <> | Date | Tue, 3 Jul 2018 11:30:38 -0700 | Subject | Re: [PATCH] refcount: always allow checked forms |
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On Tue, Jul 3, 2018 at 3:01 AM, Mark Rutland <mark.rutland@arm.com> wrote: > In many cases, it would be useful to be able to use the full > sanity-checked refcount helpers regardless of CONFIG_REFCOUNT_FULL, as > this would help to avoid duplicate warnings where callers try to > sanity-check refcount manipulation. > > This patch refactors things such that the full refcount helpers were > always built, as refcount_${op}_checked(), such that they can be used > regardless of CONFIG_REFCOUNT_FULL. This will allow code which *always* > wants a checked refcount to opt-in, avoiding the need to duplicate the > logic for warnings. > > There should be no functional change as a result of this patch. > > Signed-off-by: Mark Rutland <mark.rutland@arm.com> > Cc: Boqun Feng <boqun.feng@gmail.com> > Cc: David Sterba <dsterba@suse.com> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Kees Cook <keescook@chromium.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Will Deacon <will.deacon@arm.com>
Looks good to me! Thanks for doing this. :)
Acked-by: Kees Cook <keescook@chromium.org>
> --- > include/linux/refcount.h | 27 +++++++++++++++++------- > lib/refcount.c | 53 +++++++++++++++++++++++------------------------- > 2 files changed, 45 insertions(+), 35 deletions(-) > > Dave pointed out that it would be useful to be able to opt-in to full checks > regardless of CONFIG_REFCOUNT_FULL, so that we can simplify callsites where we > always want checks. I've spotted a few of these in code which is still awaiting > conversion.
Yeah, I need to go through the cocci output -- Elena had several outstanding patches that never got picked up.
> I'm assuming that the atomics group is intended to own the refcount code, even > though this isn't currently the case in MAINTAINERS.
That's how it has landed in the past, yes, but if there is a dependency on these for code that will use it, maybe it should go that way?
-Kees
> > Mark. > > diff --git a/include/linux/refcount.h b/include/linux/refcount.h > index a685da2c4522..b505f75ccf68 100644 > --- a/include/linux/refcount.h > +++ b/include/linux/refcount.h > @@ -42,17 +42,30 @@ static inline unsigned int refcount_read(const refcount_t *r) > return atomic_read(&r->refs); > } > > +extern __must_check bool refcount_add_not_zero_checked(unsigned int i, refcount_t *r); > +extern void refcount_add_checked(unsigned int i, refcount_t *r); > + > +extern __must_check bool refcount_inc_not_zero_checked(refcount_t *r); > +extern void refcount_inc_checked(refcount_t *r); > + > +extern __must_check bool refcount_sub_and_test_checked(unsigned int i, refcount_t *r); > + > +extern __must_check bool refcount_dec_and_test_checked(refcount_t *r); > +extern void refcount_dec_checked(refcount_t *r); > + > #ifdef CONFIG_REFCOUNT_FULL > -extern __must_check bool refcount_add_not_zero(unsigned int i, refcount_t *r); > -extern void refcount_add(unsigned int i, refcount_t *r); > > -extern __must_check bool refcount_inc_not_zero(refcount_t *r); > -extern void refcount_inc(refcount_t *r); > +#define refcount_add_not_zero refcount_add_not_zero_checked > +#define refcount_add refcount_add_checked > + > +#define refcount_inc_not_zero refcount_inc_not_zero_checked > +#define refcount_inc refcount_inc_checked > + > +#define refcount_sub_and_test refcount_sub_and_test_checked > > -extern __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r); > +#define refcount_dec_and_test refcount_dec_and_test_checked > +#define refcount_dec refcount_dec_checked > > -extern __must_check bool refcount_dec_and_test(refcount_t *r); > -extern void refcount_dec(refcount_t *r); > #else > # ifdef CONFIG_ARCH_HAS_REFCOUNT > # include <asm/refcount.h> > diff --git a/lib/refcount.c b/lib/refcount.c > index d3b81cefce91..3d514f915999 100644 > --- a/lib/refcount.c > +++ b/lib/refcount.c > @@ -38,10 +38,8 @@ > #include <linux/refcount.h> > #include <linux/bug.h> > > -#ifdef CONFIG_REFCOUNT_FULL > - > /** > - * refcount_add_not_zero - add a value to a refcount unless it is 0 > + * refcount_add_not_zero_checked - add a value to a refcount unless it is 0 > * @i: the value to add to the refcount > * @r: the refcount > * > @@ -58,7 +56,7 @@ > * > * Return: false if the passed refcount is 0, true otherwise > */ > -bool refcount_add_not_zero(unsigned int i, refcount_t *r) > +bool refcount_add_not_zero_checked(unsigned int i, refcount_t *r) > { > unsigned int new, val = atomic_read(&r->refs); > > @@ -79,10 +77,10 @@ bool refcount_add_not_zero(unsigned int i, refcount_t *r) > > return true; > } > -EXPORT_SYMBOL(refcount_add_not_zero); > +EXPORT_SYMBOL(refcount_add_not_zero_checked); > > /** > - * refcount_add - add a value to a refcount > + * refcount_add_checked - add a value to a refcount > * @i: the value to add to the refcount > * @r: the refcount > * > @@ -97,14 +95,14 @@ EXPORT_SYMBOL(refcount_add_not_zero); > * cases, refcount_inc(), or one of its variants, should instead be used to > * increment a reference count. > */ > -void refcount_add(unsigned int i, refcount_t *r) > +void refcount_add_checked(unsigned int i, refcount_t *r) > { > - WARN_ONCE(!refcount_add_not_zero(i, r), "refcount_t: addition on 0; use-after-free.\n"); > + WARN_ONCE(!refcount_add_not_zero_checked(i, r), "refcount_t: addition on 0; use-after-free.\n"); > } > -EXPORT_SYMBOL(refcount_add); > +EXPORT_SYMBOL(refcount_add_checked); > > /** > - * refcount_inc_not_zero - increment a refcount unless it is 0 > + * refcount_inc_not_zero_checked - increment a refcount unless it is 0 > * @r: the refcount to increment > * > * Similar to atomic_inc_not_zero(), but will saturate at UINT_MAX and WARN. > @@ -115,7 +113,7 @@ EXPORT_SYMBOL(refcount_add); > * > * Return: true if the increment was successful, false otherwise > */ > -bool refcount_inc_not_zero(refcount_t *r) > +bool refcount_inc_not_zero_checked(refcount_t *r) > { > unsigned int new, val = atomic_read(&r->refs); > > @@ -134,10 +132,10 @@ bool refcount_inc_not_zero(refcount_t *r) > > return true; > } > -EXPORT_SYMBOL(refcount_inc_not_zero); > +EXPORT_SYMBOL(refcount_inc_not_zero_checked); > > /** > - * refcount_inc - increment a refcount > + * refcount_inc_checked - increment a refcount > * @r: the refcount to increment > * > * Similar to atomic_inc(), but will saturate at UINT_MAX and WARN. > @@ -148,14 +146,14 @@ EXPORT_SYMBOL(refcount_inc_not_zero); > * Will WARN if the refcount is 0, as this represents a possible use-after-free > * condition. > */ > -void refcount_inc(refcount_t *r) > +void refcount_inc_chcked(refcount_t *r) > { > - WARN_ONCE(!refcount_inc_not_zero(r), "refcount_t: increment on 0; use-after-free.\n"); > + WARN_ONCE(!refcount_inc_not_zero_checked(r), "refcount_t: increment on 0; use-after-free.\n"); > } > -EXPORT_SYMBOL(refcount_inc); > +EXPORT_SYMBOL(refcount_inc_checked); > > /** > - * refcount_sub_and_test - subtract from a refcount and test if it is 0 > + * refcount_sub_and_test_checked - subtract from a refcount and test if it is 0 > * @i: amount to subtract from the refcount > * @r: the refcount > * > @@ -174,7 +172,7 @@ EXPORT_SYMBOL(refcount_inc); > * > * Return: true if the resulting refcount is 0, false otherwise > */ > -bool refcount_sub_and_test(unsigned int i, refcount_t *r) > +bool refcount_sub_and_test_checked(unsigned int i, refcount_t *r) > { > unsigned int new, val = atomic_read(&r->refs); > > @@ -192,10 +190,10 @@ bool refcount_sub_and_test(unsigned int i, refcount_t *r) > > return !new; > } > -EXPORT_SYMBOL(refcount_sub_and_test); > +EXPORT_SYMBOL(refcount_sub_and_test_checked); > > /** > - * refcount_dec_and_test - decrement a refcount and test if it is 0 > + * refcount_dec_and_test_checked - decrement a refcount and test if it is 0 > * @r: the refcount > * > * Similar to atomic_dec_and_test(), it will WARN on underflow and fail to > @@ -207,14 +205,14 @@ EXPORT_SYMBOL(refcount_sub_and_test); > * > * Return: true if the resulting refcount is 0, false otherwise > */ > -bool refcount_dec_and_test(refcount_t *r) > +bool refcount_dec_and_test_checked(refcount_t *r) > { > - return refcount_sub_and_test(1, r); > + return refcount_sub_and_test_checked(1, r); > } > -EXPORT_SYMBOL(refcount_dec_and_test); > +EXPORT_SYMBOL(refcount_dec_and_test_checked); > > /** > - * refcount_dec - decrement a refcount > + * refcount_dec_checked - decrement a refcount > * @r: the refcount > * > * Similar to atomic_dec(), it will WARN on underflow and fail to decrement > @@ -223,12 +221,11 @@ EXPORT_SYMBOL(refcount_dec_and_test); > * Provides release memory ordering, such that prior loads and stores are done > * before. > */ > -void refcount_dec(refcount_t *r) > +void refcount_dec_checked(refcount_t *r) > { > - WARN_ONCE(refcount_dec_and_test(r), "refcount_t: decrement hit 0; leaking memory.\n"); > + WARN_ONCE(refcount_dec_and_test_checked(r), "refcount_t: decrement hit 0; leaking memory.\n"); > } > -EXPORT_SYMBOL(refcount_dec); > -#endif /* CONFIG_REFCOUNT_FULL */ > +EXPORT_SYMBOL(refcount_dec_checked); > > /** > * refcount_dec_if_one - decrement a refcount if it is 1 > -- > 2.11.0 >
-- Kees Cook Pixel Security
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