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Kernel: Implement recursion limit on path resolution

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Cautiously use 5 as a limit for now so that we don't blow the stack.
This can be increased in the future if we are sure that we won't be
blowing the stack, or if the implementation is changed to not use
recursion :^)
This commit is contained in:
Shannon Booth 2019-12-24 22:39:21 +13:00 committed by Andreas Kling
parent 3623e35978
commit 0e45b9423b
Notes: sideshowbarker 2024-07-19 10:42:15 +09:00 
Author: https://github.com/shannonbooth
Commit: https://github.com/SerenityOS/serenity/commit/0e45b9423b0
Pull-request: https://github.com/SerenityOS/serenity/pull/911
Reviewed-by: https://github.com/awesomekling
2 changed files with 8 additions and 11 deletions
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17
Kernel/FileSystem/VirtualFileSystem.cpp
View File

@ -11,6 +11,7 @@
//#define VFS_DEBUG
static VFS* s_the;
static constexpr int symlink_recursion_limit { 5 }; // FIXME: increase?
VFS& VFS::the()
{
@ -615,7 +616,6 @@ InodeIdentifier VFS::Mount::host() const
return m_host_custody->inode().identifier();
}
void VFS::for_each_mount(Function<void(const Mount&)> callback) const
{
for (auto& mount : m_mounts) {
@ -635,10 +635,12 @@ Custody& VFS::root_custody()
return *m_root_custody;
}
KResultOr<NonnullRefPtr<Custody>> VFS::resolve_path(StringView path, Custody& base, RefPtr<Custody>* parent_custody, int options)
KResultOr<NonnullRefPtr<Custody>> VFS::resolve_path(StringView path, Custody& base, RefPtr<Custody>* parent_custody, int options, int symlink_recursion_level)
{
// FIXME: resolve_path currently doesn't deal with .. and . . If path is ../. and base is /home/anon, it returns
// /home/anon/../. instead of /home .
if (symlink_recursion_level >= symlink_recursion_limit)
return KResult(-ELOOP);
if (path.is_empty())
return KResult(-EINVAL);
@ -712,13 +714,8 @@ KResultOr<NonnullRefPtr<Custody>> VFS::resolve_path(StringView path, Custody& ba
if (!symlink_contents)
return KResult(-ENOENT);
// FIXME: We should limit the recursion here and return -ELOOP if it goes to deep.
auto symlink_target = resolve_path(
StringView(symlink_contents.data(),
symlink_contents.size()),
current_parent,
parent_custody,
options);
auto symlink_path = StringView(symlink_contents.data(), symlink_contents.size());
auto symlink_target = resolve_path(symlink_path, current_parent, parent_custody, options, symlink_recursion_level + 1);
if (symlink_target.is_error())
return symlink_target;
@ -731,7 +728,7 @@ KResultOr<NonnullRefPtr<Custody>> VFS::resolve_path(StringView path, Custody& ba
return symlink_target;
StringView remaining_path = path.substring_view_starting_from_substring(parts[i + 1]);
return resolve_path(remaining_path, *symlink_target.value(), parent_custody, options);
return resolve_path(remaining_path, *symlink_target.value(), parent_custody, options, symlink_recursion_level + 1);
}
}
return custody_chain.last();

2
Kernel/FileSystem/VirtualFileSystem.h
View File

@ -88,7 +88,7 @@ public:
void sync();
Custody& root_custody();
KResultOr<NonnullRefPtr<Custody>> resolve_path(StringView path, Custody& base, RefPtr<Custody>* parent = nullptr, int options = 0);
KResultOr<NonnullRefPtr<Custody>> resolve_path(StringView path, Custody& base, RefPtr<Custody>* parent = nullptr, int options = 0, int symlink_recursion_level = 0);
private:
friend class FileDescription;