Commit afed7bcf authored by Mark Rutland's avatar Mark Rutland Committed by Ingo Molnar
Browse files

locking/refcount: Always allow checked forms 



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: default avatarMark Rutland <mark.rutland@arm.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180711093607.1644-1-mark.rutland@arm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 75a040ff

include/linux/refcount.h

+20 −7
Original line number Diff line number Diff line
@@ -43,17 +43,30 @@ 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>

lib/refcount.c

+25 −28
Original line number Diff line number Diff line
@@ -40,10 +40,8 @@ 
#include <linux/spinlock.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

 *
@@ -60,7 +58,7 @@ 
 *

 * 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);
@@ -81,10 +79,10 @@ 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

 *
@@ -99,14 +97,14 @@ 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.
@@ -117,7 +115,7 @@ 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);
@@ -136,10 +134,10 @@ 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.
@@ -150,14 +148,14 @@ 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_checked(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

 *
@@ -176,7 +174,7 @@ 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);
@@ -194,10 +192,10 @@ 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
@@ -209,14 +207,14 @@ 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
@@ -225,12 +223,11 @@ 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

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