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Merge branch 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

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Pull exec-update-lock update from Eric Biederman:
 "The key point of this is to transform exec_update_mutex into a
  rw_semaphore so readers can be separated from writers.

  This makes it easier to understand what the holders of the lock are
  doing, and makes it harder to contend or deadlock on the lock.

  The real deadlock fix wound up in perf_event_open"

* 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  exec: Transform exec_update_mutex into a rw_semaphore
This commit is contained in:
Linus Torvalds
2020-12-15 19:36:48 -08:00
parent faf145d6f3 f7cfd871ae
commit d01e7f10da
8 changed files with 44 additions and 43 deletions
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6
kernel/fork.c
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@@ -1225,7 +1225,7 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
struct mm_struct *mm;
int err;
err = mutex_lock_killable(&task->signal->exec_update_mutex);
err = down_read_killable(&task->signal->exec_update_lock);
if (err)
return ERR_PTR(err);
@@ -1235,7 +1235,7 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
mmput(mm);
mm = ERR_PTR(-EACCES);
}
mutex_unlock(&task->signal->exec_update_mutex);
up_read(&task->signal->exec_update_lock);
return mm;
}
@@ -1595,7 +1595,7 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
sig->oom_score_adj_min = current->signal->oom_score_adj_min;
mutex_init(&sig->cred_guard_mutex);
mutex_init(&sig->exec_update_mutex);
init_rwsem(&sig->exec_update_lock);
return 0;
}