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Kernel: Fix ProcFS returning Inodes that are being deleted

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There is a window between dropping the last reference and removing
a ProcFSInode from the lookup map. So, when looking up we need to
check if that Inode is being destructed.
This commit is contained in:
Tom 2021-01-02 19:19:06 -07:00 • committed by Andreas Kling
parent 5cbcb35d34
commit c943ca95c4
1 changed files with 16 additions and 6 deletions
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22
Kernel/FileSystem/ProcFS.cpp
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@ -1101,12 +1101,20 @@ RefPtr<Inode> ProcFS::get_inode(InodeIdentifier inode_id) const
LOCKER(m_inodes_lock); LOCKER(m_inodes_lock);
auto it = m_inodes.find(inode_id.index()); auto it = m_inodes.find(inode_id.index());
if (it == m_inodes.end()) { if (it != m_inodes.end()) {
auto inode = adopt(*new ProcFSInode(const_cast<ProcFS&>(*this), inode_id.index())); // It's possible that the ProcFSInode ref count was dropped to 0 or
m_inodes.set(inode_id.index(), inode.ptr()); // the ~ProcFSInode destructor is even running already, but blocked
return inode; // from removing it from this map. So we need to *try* to ref it,
// and if that fails we cannot return this instance anymore and just
// create a new one.
if (it->value->try_ref())
return adopt(*it->value);
// We couldn't ref it, so just create a new one and replace the entry
} }
return (*it).value; auto inode = adopt(*new ProcFSInode(const_cast<ProcFS&>(*this), inode_id.index()));
auto result = m_inodes.set(inode_id.index(), inode.ptr());
ASSERT(result == ((it == m_inodes.end()) ? AK::HashSetResult::InsertedNewEntry : AK::HashSetResult::ReplacedExistingEntry));
return inode;
} }
ProcFSInode::ProcFSInode(ProcFS& fs, unsigned index) ProcFSInode::ProcFSInode(ProcFS& fs, unsigned index)
@ -1117,7 +1125,9 @@ ProcFSInode::ProcFSInode(ProcFS& fs, unsigned index)
ProcFSInode::~ProcFSInode() ProcFSInode::~ProcFSInode()
{ {
LOCKER(fs().m_inodes_lock); LOCKER(fs().m_inodes_lock);
fs().m_inodes.remove(index()); auto it = fs().m_inodes.find(index());
if (it != fs().m_inodes.end() && it->value == this)
fs().m_inodes.remove(it);
} }
InodeMetadata ProcFSInode::metadata() const InodeMetadata ProcFSInode::metadata() const