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futex: Move futex exit handling into futex code

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commit ba31c1a485 upstream.

The futex exit handling is #ifdeffed into mm_release() which is not pretty
to begin with. But upcoming changes to address futex exit races need to add
more functionality to this exit code.

Split it out into a function, move it into futex code and make the various
futex exit functions static.

Preparatory only and no functional change.

Folded build fix from Borislav.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191106224556.049705556@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Thomas Gleixner
2021-02-01 10:01:33 +00:00
committed by Chris
parent 73380062b0
commit 82125a1e08
4 changed files with 47 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/compat.h
View File

@@ -311,8 +311,6 @@ struct compat_kexec_segment;
struct compat_mq_attr;
struct compat_msgbuf;
extern void compat_exit_robust_list(struct task_struct *curr);
asmlinkage long
compat_sys_set_robust_list(struct compat_robust_list_head __user *head,
compat_size_t len);

26
include/linux/futex.h
View File

@@ -1,6 +1,8 @@
#ifndef _LINUX_FUTEX_H
#define _LINUX_FUTEX_H
#include <linux/sched.h>
#include <uapi/linux/futex.h>
struct inode;
@@ -53,14 +55,22 @@ union futex_key {
#define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = 0ULL } }
#ifdef CONFIG_FUTEX
extern void exit_robust_list(struct task_struct *curr);
extern void exit_pi_state_list(struct task_struct *curr);
static inline void futex_init_task(struct task_struct *tsk)
{
tsk->robust_list = NULL;
#ifdef CONFIG_COMPAT
tsk->compat_robust_list = NULL;
#endif
INIT_LIST_HEAD(&tsk->pi_state_list);
tsk->pi_state_cache = NULL;
}
void futex_mm_release(struct task_struct *tsk);
long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
u32 __user *uaddr2, u32 val2, u32 val3);
#else
static inline void exit_robust_list(struct task_struct *curr)
{
}
static inline void exit_pi_state_list(struct task_struct *curr)
{
}
static inline void futex_init_task(struct task_struct *tsk) { }
static inline void futex_mm_release(struct task_struct *tsk) { }
#endif
#endif

25
kernel/fork.c
View File

@@ -1106,20 +1106,7 @@ static int wait_for_vfork_done(struct task_struct *child,
void mm_release(struct task_struct *tsk, struct mm_struct *mm)
{
/* Get rid of any futexes when releasing the mm */
#ifdef CONFIG_FUTEX
if (unlikely(tsk->robust_list)) {
exit_robust_list(tsk);
tsk->robust_list = NULL;
}
#ifdef CONFIG_COMPAT
if (unlikely(tsk->compat_robust_list)) {
compat_exit_robust_list(tsk);
tsk->compat_robust_list = NULL;
}
#endif
if (unlikely(!list_empty(&tsk->pi_state_list)))
exit_pi_state_list(tsk);
#endif
futex_mm_release(tsk);
uprobe_free_utask(tsk);
@@ -1729,14 +1716,8 @@ static __latent_entropy struct task_struct *copy_process(
#ifdef CONFIG_BLOCK
p->plug = NULL;
#endif
#ifdef CONFIG_FUTEX
p->robust_list = NULL;
#ifdef CONFIG_COMPAT
p->compat_robust_list = NULL;
#endif
INIT_LIST_HEAD(&p->pi_state_list);
p->pi_state_cache = NULL;
#endif
futex_init_task(p);
/*
* sigaltstack should be cleared when sharing the same VM
*/

28
kernel/futex.c
View File

@@ -339,6 +339,12 @@ static inline bool should_fail_futex(bool fshared)
}
#endif /* CONFIG_FAIL_FUTEX */
#ifdef CONFIG_COMPAT
static void compat_exit_robust_list(struct task_struct *curr);
#else
static inline void compat_exit_robust_list(struct task_struct *curr) { }
#endif
static inline void futex_get_mm(union futex_key *key)
{
atomic_inc(&key->private.mm->mm_count);
@@ -894,7 +900,7 @@ static struct task_struct * futex_find_get_task(pid_t pid)
* Kernel cleans up PI-state, but userspace is likely hosed.
* (Robust-futex cleanup is separate and might save the day for userspace.)
*/
void exit_pi_state_list(struct task_struct *curr)
static void exit_pi_state_list(struct task_struct *curr)
{
struct list_head *next, *head = &curr->pi_state_list;
struct futex_pi_state *pi_state;
@@ -3201,7 +3207,7 @@ static inline int fetch_robust_entry(struct robust_list __user **entry,
*
* We silently return on any sign of list-walking problem.
*/
void exit_robust_list(struct task_struct *curr)
static void exit_robust_list(struct task_struct *curr)
{
struct robust_list_head __user *head = curr->robust_list;
struct robust_list __user *entry, *next_entry, *pending;
@@ -3264,6 +3270,24 @@ void exit_robust_list(struct task_struct *curr)
curr, pip);
}
void futex_mm_release(struct task_struct *tsk)
{
if (unlikely(tsk->robust_list)) {
exit_robust_list(tsk);
tsk->robust_list = NULL;
}
#ifdef CONFIG_COMPAT
if (unlikely(tsk->compat_robust_list)) {
compat_exit_robust_list(tsk);
tsk->compat_robust_list = NULL;
}
#endif
if (unlikely(!list_empty(&tsk->pi_state_list)))
exit_pi_state_list(tsk);
}
long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
u32 __user *uaddr2, u32 val2, u32 val3)
{