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97a1420adf
In preparation for changing the saturation point of REFCOUNT_FULL to INT_MIN/2, change the type of integer operands passed into the API from 'unsigned int' to 'int' so that we can avoid casting during comparisons when we don't want to fall foul of C integral conversion rules for signed and unsigned types. Since the kernel is compiled with '-fno-strict-overflow', we don't need to worry about the UB introduced by signed overflow here. Furthermore, we're already making heavy use of the atomic_t API, which operates exclusively on signed types. Signed-off-by: Will Deacon <will@kernel.org> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Hanjun Guo <guohanjun@huawei.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Elena Reshetova <elena.reshetova@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20191121115902.2551-3-will@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
127 lines
3.3 KiB
C
127 lines
3.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_REFCOUNT_H
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#define _LINUX_REFCOUNT_H
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#include <linux/atomic.h>
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#include <linux/compiler.h>
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#include <linux/limits.h>
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#include <linux/spinlock_types.h>
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struct mutex;
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/**
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* struct refcount_t - variant of atomic_t specialized for reference counts
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* @refs: atomic_t counter field
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*
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* The counter saturates at REFCOUNT_SATURATED and will not move once
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* there. This avoids wrapping the counter and causing 'spurious'
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* use-after-free bugs.
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*/
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typedef struct refcount_struct {
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atomic_t refs;
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} refcount_t;
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#define REFCOUNT_INIT(n) { .refs = ATOMIC_INIT(n), }
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/**
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* refcount_set - set a refcount's value
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* @r: the refcount
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* @n: value to which the refcount will be set
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*/
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static inline void refcount_set(refcount_t *r, int n)
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{
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atomic_set(&r->refs, n);
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}
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/**
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* refcount_read - get a refcount's value
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* @r: the refcount
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*
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* Return: the refcount's value
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*/
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static inline unsigned int refcount_read(const refcount_t *r)
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{
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return atomic_read(&r->refs);
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}
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extern __must_check bool refcount_add_not_zero_checked(int i, refcount_t *r);
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extern void refcount_add_checked(int i, refcount_t *r);
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extern __must_check bool refcount_inc_not_zero_checked(refcount_t *r);
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extern void refcount_inc_checked(refcount_t *r);
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extern __must_check bool refcount_sub_and_test_checked(int i, refcount_t *r);
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extern __must_check bool refcount_dec_and_test_checked(refcount_t *r);
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extern void refcount_dec_checked(refcount_t *r);
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#ifdef CONFIG_REFCOUNT_FULL
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#define REFCOUNT_MAX (UINT_MAX - 1)
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#define REFCOUNT_SATURATED UINT_MAX
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#define refcount_add_not_zero refcount_add_not_zero_checked
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#define refcount_add refcount_add_checked
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#define refcount_inc_not_zero refcount_inc_not_zero_checked
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#define refcount_inc refcount_inc_checked
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#define refcount_sub_and_test refcount_sub_and_test_checked
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#define refcount_dec_and_test refcount_dec_and_test_checked
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#define refcount_dec refcount_dec_checked
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#else
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#define REFCOUNT_MAX INT_MAX
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#define REFCOUNT_SATURATED (INT_MIN / 2)
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# ifdef CONFIG_ARCH_HAS_REFCOUNT
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# include <asm/refcount.h>
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# else
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static inline __must_check bool refcount_add_not_zero(int i, refcount_t *r)
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{
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return atomic_add_unless(&r->refs, i, 0);
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}
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static inline void refcount_add(int i, refcount_t *r)
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{
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atomic_add(i, &r->refs);
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}
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static inline __must_check bool refcount_inc_not_zero(refcount_t *r)
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{
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return atomic_add_unless(&r->refs, 1, 0);
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}
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static inline void refcount_inc(refcount_t *r)
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{
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atomic_inc(&r->refs);
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}
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static inline __must_check bool refcount_sub_and_test(int i, refcount_t *r)
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{
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return atomic_sub_and_test(i, &r->refs);
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}
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static inline __must_check bool refcount_dec_and_test(refcount_t *r)
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{
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return atomic_dec_and_test(&r->refs);
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}
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static inline void refcount_dec(refcount_t *r)
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{
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atomic_dec(&r->refs);
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}
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# endif /* !CONFIG_ARCH_HAS_REFCOUNT */
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#endif /* CONFIG_REFCOUNT_FULL */
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extern __must_check bool refcount_dec_if_one(refcount_t *r);
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extern __must_check bool refcount_dec_not_one(refcount_t *r);
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extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
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extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
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extern __must_check bool refcount_dec_and_lock_irqsave(refcount_t *r,
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spinlock_t *lock,
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unsigned long *flags);
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#endif /* _LINUX_REFCOUNT_H */
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