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fdb71cdf8f
This adds support for MS_RDONLY, a mount flag that tells the kernel to disallow any attempts to write to the newly mounted filesystem. As this flag is per-mount, and different mounts of the same filesystems (such as in case of bind mounts) can have different mutability settings, you have to go though a custody to find out if the filesystem is mounted read-only, instead of just asking the filesystem itself whether it's inherently read-only. This also adds a lot of checks we were previously missing; and moves some of them to happen after more specific checks (such as regular permission checks). One outstanding hole in this system is sys$mprotect(PROT_WRITE), as there's no way we can know if the original file description this region has been mounted from had been opened through a readonly mount point. Currently, we always allow such sys$mprotect() calls to succeed, which effectively allows anyone to circumvent the effect of MS_RDONLY. We should solve this one way or another.
69 lines
2.4 KiB
C++
69 lines
2.4 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/RefCounted.h>
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#include <AK/RefPtr.h>
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#include <AK/String.h>
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#include <Kernel/Forward.h>
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#include <Kernel/Heap/SlabAllocator.h>
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namespace Kernel {
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// FIXME: Custody needs some locking.
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class Custody : public RefCounted<Custody> {
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MAKE_SLAB_ALLOCATED(Custody)
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public:
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static NonnullRefPtr<Custody> create(Custody* parent, const StringView& name, Inode& inode, int mount_flags)
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{
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return adopt(*new Custody(parent, name, inode, mount_flags));
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}
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~Custody();
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Custody* parent() { return m_parent.ptr(); }
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const Custody* parent() const { return m_parent.ptr(); }
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Inode& inode() { return *m_inode; }
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const Inode& inode() const { return *m_inode; }
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const String& name() const { return m_name; }
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String absolute_path() const;
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int mount_flags() const { return m_mount_flags; }
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bool is_readonly() const;
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private:
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Custody(Custody* parent, const StringView& name, Inode&, int mount_flags);
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RefPtr<Custody> m_parent;
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String m_name;
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NonnullRefPtr<Inode> m_inode;
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int m_mount_flags { 0 };
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};
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}
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