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Kernel: Make ProcessGroup a ListedRefCounted and fix two races

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This closes two race windows:

- ProcessGroup removed itself from the "all process groups" list in its
  destructor. It was possible to walk the list between the last unref()
  and the destructor invocation, and grab a pointer to a ProcessGroup
  that was about to get deleted.

- sys$setsid() could end up creating a process group that already
  existed, as there was a race window between checking if the PGID
  is used, and actually creating a ProcessGroup with that PGID.
This commit is contained in:
Andreas Kling 2023-04-04 16:38:46 +02:00
parent 37bfc36601
commit 3e30d9bc99
3 changed files with 29 additions and 36 deletions
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16
Kernel/ProcessGroup.h
View file

@ -1,15 +1,15 @@
/*
* Copyright (c) 2020, the SerenityOS developers.
* Copyright (c) 2020-2023, the SerenityOS developers.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/AtomicRefCounted.h>
#include <AK/IntrusiveList.h>
#include <AK/RefPtr.h>
#include <Kernel/Forward.h>
#include <Kernel/Library/ListedRefCounted.h>
#include <Kernel/Library/LockWeakable.h>
#include <Kernel/Locking/SpinlockProtected.h>
#include <Kernel/UnixTypes.h>
@ -17,7 +17,7 @@
namespace Kernel {
class ProcessGroup
: public AtomicRefCounted<ProcessGroup>
: public ListedRefCounted<ProcessGroup, LockType::Spinlock>
, public LockWeakable<ProcessGroup> {
AK_MAKE_NONMOVABLE(ProcessGroup);
@ -26,7 +26,7 @@ class ProcessGroup
public:
~ProcessGroup();
static ErrorOr<NonnullRefPtr<ProcessGroup>> create(ProcessGroupID);
static ErrorOr<NonnullRefPtr<ProcessGroup>> create_if_unused_pgid(ProcessGroupID);
static ErrorOr<NonnullRefPtr<ProcessGroup>> find_or_create(ProcessGroupID);
static RefPtr<ProcessGroup> from_pgid(ProcessGroupID);
@ -38,13 +38,13 @@ private:
{
}
IntrusiveListNode<ProcessGroup> m_list_node;
ProcessGroupID m_pgid;
mutable IntrusiveListNode<ProcessGroup> m_list_node;
public:
using List = IntrusiveList<&ProcessGroup::m_list_node>;
using AllInstancesList = IntrusiveList<&ProcessGroup::m_list_node>;
static SpinlockProtected<AllInstancesList, LockRank::None>& all_instances();
};
SpinlockProtected<ProcessGroup::List, LockRank::None>& process_groups();
}