forked from mirrors/linux
8019ad13ef
As reported by Jann, ihold() does not in fact guarantee inode persistence. And instead of making it so, replace the usage of inode pointers with a per boot, machine wide, unique inode identifier. This sequence number is global, but shared (file backed) futexes are rare enough that this should not become a performance issue. Reported-by: Jann Horn <jannh@google.com> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
93 lines
2.4 KiB
C
93 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_FUTEX_H
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#define _LINUX_FUTEX_H
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#include <linux/sched.h>
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#include <linux/ktime.h>
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#include <uapi/linux/futex.h>
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struct inode;
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struct mm_struct;
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struct task_struct;
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/*
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* Futexes are matched on equal values of this key.
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* The key type depends on whether it's a shared or private mapping.
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* Don't rearrange members without looking at hash_futex().
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*
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* offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
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* We use the two low order bits of offset to tell what is the kind of key :
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* 00 : Private process futex (PTHREAD_PROCESS_PRIVATE)
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* (no reference on an inode or mm)
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* 01 : Shared futex (PTHREAD_PROCESS_SHARED)
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* mapped on a file (reference on the underlying inode)
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* 10 : Shared futex (PTHREAD_PROCESS_SHARED)
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* (but private mapping on an mm, and reference taken on it)
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*/
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#define FUT_OFF_INODE 1 /* We set bit 0 if key has a reference on inode */
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#define FUT_OFF_MMSHARED 2 /* We set bit 1 if key has a reference on mm */
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union futex_key {
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struct {
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u64 i_seq;
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unsigned long pgoff;
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unsigned int offset;
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} shared;
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struct {
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union {
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struct mm_struct *mm;
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u64 __tmp;
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};
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unsigned long address;
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unsigned int offset;
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} private;
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struct {
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u64 ptr;
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unsigned long word;
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unsigned int offset;
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} both;
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};
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#define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = 0ULL } }
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#ifdef CONFIG_FUTEX
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enum {
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FUTEX_STATE_OK,
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FUTEX_STATE_EXITING,
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FUTEX_STATE_DEAD,
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};
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static inline void futex_init_task(struct task_struct *tsk)
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{
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tsk->robust_list = NULL;
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#ifdef CONFIG_COMPAT
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tsk->compat_robust_list = NULL;
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#endif
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INIT_LIST_HEAD(&tsk->pi_state_list);
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tsk->pi_state_cache = NULL;
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tsk->futex_state = FUTEX_STATE_OK;
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mutex_init(&tsk->futex_exit_mutex);
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}
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void futex_exit_recursive(struct task_struct *tsk);
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void futex_exit_release(struct task_struct *tsk);
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void futex_exec_release(struct task_struct *tsk);
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long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
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u32 __user *uaddr2, u32 val2, u32 val3);
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#else
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static inline void futex_init_task(struct task_struct *tsk) { }
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static inline void futex_exit_recursive(struct task_struct *tsk) { }
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static inline void futex_exit_release(struct task_struct *tsk) { }
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static inline void futex_exec_release(struct task_struct *tsk) { }
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static inline long do_futex(u32 __user *uaddr, int op, u32 val,
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ktime_t *timeout, u32 __user *uaddr2,
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u32 val2, u32 val3)
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{
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return -EINVAL;
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}
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#endif
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#endif
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