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locking/refcount: Always allow checked forms

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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>
Reviewed-by: David Sterba <dsterba@suse.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Will 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Mark Rutland 2018-07-11 10:36:07 +01:00 committed by Ingo Molnar
parent 75a040ff14
commit afed7bcf94
2 changed files with 45 additions and 35 deletions
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27
include/linux/refcount.h
View File

@ -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
extern __must_check bool refcount_sub_and_test(unsigned int i, refcount_t *r);
#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
#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>

53
lib/refcount.c
View File

@ -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