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Kernel: sys$munmap() region splitting did not preserve "shared" flag

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This was exploitable since the shared flag determines whether inode
permission checks are applied in sys$mprotect().

The bug was pretty hard to spot due to default arguments being used
instead. This patch removes the default arguments to make explicit
at each call site what's being done.
This commit is contained in:
Andreas Kling 2021-01-26 16:56:34 +01:00
parent e7183cc762
commit a131927c75
4 changed files with 9 additions and 6 deletions
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6
Kernel/VM/Region.cpp
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@ -99,7 +99,8 @@ OwnPtr<Region> Region::clone(Process& new_owner)
ASSERT(vmobject().is_shared_inode());
// Create a new region backed by the same VMObject.
auto region = Region::create_user_accessible(&new_owner, m_range, m_vmobject, m_offset_in_vmobject, m_name, m_access);
auto region = Region::create_user_accessible(
&new_owner, m_range, m_vmobject, m_offset_in_vmobject, m_name, m_access, m_cacheable, m_shared);
if (m_vmobject->is_anonymous())
region->copy_purgeable_page_ranges(*this);
region->set_mmap(m_mmap);
@ -116,7 +117,8 @@ OwnPtr<Region> Region::clone(Process& new_owner)
// Set up a COW region. The parent (this) region becomes COW as well!
remap();
auto clone_region = Region::create_user_accessible(&new_owner, m_range, vmobject_clone.release_nonnull(), m_offset_in_vmobject, m_name, m_access);
auto clone_region = Region::create_user_accessible(
&new_owner, m_range, vmobject_clone.release_nonnull(), m_offset_in_vmobject, m_name, m_access, m_cacheable, m_shared);
if (m_vmobject->is_anonymous())
clone_region->copy_purgeable_page_ranges(*this);
if (m_stack) {