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Kernel: Actually check Process unveil data when creating perfcore dump

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Before of this patch, we looked at the unveil data of the FinalizerTask,
which naturally doesn't have any unveil restrictions, therefore allowing
an unveil bypass for a process that enabled performance coredumps.

To ensure we always check the dumped process unveil data, an option to
pass a Process& has been added to a couple of methods in the class of
VirtualFileSystem.
This commit is contained in:
Liav A 2023-03-04 20:01:54 +02:00 committed by Sam Atkins
parent 882dcfaddb
commit 39de5b7f82
Notes: sideshowbarker 2024-07-17 08:59:18 +09:00 
Author: https://github.com/supercomputer7
Commit: https://github.com/SerenityOS/serenity/commit/39de5b7f82
Pull-request: https://github.com/SerenityOS/serenity/pull/17716
Issue: https://github.com/SerenityOS/serenity/issues/15996
3 changed files with 46 additions and 17 deletions
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54
Kernel/FileSystem/VirtualFileSystem.cpp
View File

@ -357,17 +357,22 @@ ErrorOr<NonnullLockRefPtr<FileBackedFileSystem>> VirtualFileSystem::find_already
}
ErrorOr<NonnullLockRefPtr<OpenFileDescription>> VirtualFileSystem::open(Credentials const& credentials, StringView path, int options, mode_t mode, Custody& base, Optional<UidAndGid> owner)
{
return open(Process::current(), credentials, path, options, mode, base, owner);
}
ErrorOr<NonnullLockRefPtr<OpenFileDescription>> VirtualFileSystem::open(Process const& process, Credentials const& credentials, StringView path, int options, mode_t mode, Custody& base, Optional<UidAndGid> owner)
{
if ((options & O_CREAT) && (options & O_DIRECTORY))
return EINVAL;
RefPtr<Custody> parent_custody;
auto custody_or_error = resolve_path(credentials, path, base, &parent_custody, options);
auto custody_or_error = resolve_path(process, credentials, path, base, &parent_custody, options);
if (custody_or_error.is_error()) {
// NOTE: ENOENT with a non-null parent custody signals us that the immediate parent
// of the file exists, but the file itself does not.
if ((options & O_CREAT) && custody_or_error.error().code() == ENOENT && parent_custody)
return create(credentials, path, options, mode, *parent_custody, move(owner));
return create(process, credentials, path, options, mode, *parent_custody, move(owner));
return custody_or_error.release_error();
}
@ -472,11 +477,16 @@ ErrorOr<void> VirtualFileSystem::mknod(Credentials const& credentials, StringVie
}
ErrorOr<NonnullLockRefPtr<OpenFileDescription>> VirtualFileSystem::create(Credentials const& credentials, StringView path, int options, mode_t mode, Custody& parent_custody, Optional<UidAndGid> owner)
{
return create(Process::current(), credentials, path, options, mode, parent_custody, owner);
}
ErrorOr<NonnullLockRefPtr<OpenFileDescription>> VirtualFileSystem::create(Process const& process, Credentials const& credentials, StringView path, int options, mode_t mode, Custody& parent_custody, Optional<UidAndGid> owner)
{
auto basename = KLexicalPath::basename(path);
auto parent_path = TRY(parent_custody.try_serialize_absolute_path());
auto full_path = TRY(KLexicalPath::try_join(parent_path->view(), basename));
TRY(validate_path_against_process_veil(full_path->view(), options));
TRY(validate_path_against_process_veil(process, full_path->view(), options));
if (!is_socket(mode) && !is_fifo(mode) && !is_block_device(mode) && !is_character_device(mode)) {
// Turn it into a regular file. (This feels rather hackish.)
@ -938,11 +948,10 @@ NonnullRefPtr<Custody> VirtualFileSystem::root_custody()
return m_root_custody.with([](auto& root_custody) -> NonnullRefPtr<Custody> { return *root_custody; });
}
UnveilNode const& VirtualFileSystem::find_matching_unveiled_path(StringView path)
UnveilNode const& VirtualFileSystem::find_matching_unveiled_path(Process const& process, StringView path)
{
auto& current_process = Process::current();
VERIFY(current_process.veil_state() != VeilState::None);
return current_process.unveil_data().with([&](auto const& unveil_data) -> UnveilNode const& {
VERIFY(process.veil_state() != VeilState::None);
return process.unveil_data().with([&](auto const& unveil_data) -> UnveilNode const& {
auto path_parts = KLexicalPath::parts(path);
return unveil_data.paths.traverse_until_last_accessible_node(path_parts.begin(), path_parts.end());
});
@ -950,15 +959,20 @@ UnveilNode const& VirtualFileSystem::find_matching_unveiled_path(StringView path
ErrorOr<void> VirtualFileSystem::validate_path_against_process_veil(Custody const& custody, int options)
{
if (Process::current().veil_state() == VeilState::None)
return {};
auto absolute_path = TRY(custody.try_serialize_absolute_path());
return validate_path_against_process_veil(absolute_path->view(), options);
return validate_path_against_process_veil(Process::current(), custody, options);
}
ErrorOr<void> VirtualFileSystem::validate_path_against_process_veil(StringView path, int options)
ErrorOr<void> VirtualFileSystem::validate_path_against_process_veil(Process const& process, Custody const& custody, int options)
{
if (Process::current().veil_state() == VeilState::None)
if (process.veil_state() == VeilState::None)
return {};
auto absolute_path = TRY(custody.try_serialize_absolute_path());
return validate_path_against_process_veil(process, absolute_path->view(), options);
}
ErrorOr<void> VirtualFileSystem::validate_path_against_process_veil(Process const& process, StringView path, int options)
{
if (process.veil_state() == VeilState::None)
return {};
VERIFY(path.starts_with('/'));
@ -972,7 +986,7 @@ ErrorOr<void> VirtualFileSystem::validate_path_against_process_veil(StringView p
return {};
#endif
auto& unveiled_path = find_matching_unveiled_path(path);
auto& unveiled_path = find_matching_unveiled_path(process, path);
if (unveiled_path.permissions() == UnveilAccess::None) {
dbgln("Rejecting path '{}' since it hasn't been unveiled.", path);
dump_backtrace();
@ -1026,12 +1040,22 @@ ErrorOr<void> VirtualFileSystem::validate_path_against_process_veil(StringView p
return {};
}
ErrorOr<void> VirtualFileSystem::validate_path_against_process_veil(StringView path, int options)
{
return validate_path_against_process_veil(Process::current(), path, options);
}
ErrorOr<NonnullRefPtr<Custody>> VirtualFileSystem::resolve_path(Credentials const& credentials, StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent, int options, int symlink_recursion_level)
{
return resolve_path(Process::current(), credentials, path, base, out_parent, options, symlink_recursion_level);
}
ErrorOr<NonnullRefPtr<Custody>> VirtualFileSystem::resolve_path(Process const& process, Credentials const& credentials, StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent, int options, int symlink_recursion_level)
{
// FIXME: The errors returned by resolve_path_without_veil can leak information about paths that are not unveiled,
// e.g. when the error is EACCESS or similar.
auto custody = TRY(resolve_path_without_veil(credentials, path, base, out_parent, options, symlink_recursion_level));
if (auto result = validate_path_against_process_veil(*custody, options); result.is_error()) {
if (auto result = validate_path_against_process_veil(process, *custody, options); result.is_error()) {
if (out_parent)
out_parent->clear();
return result.release_error();

7
Kernel/FileSystem/VirtualFileSystem.h
View File

@ -61,7 +61,9 @@ public:
ErrorOr<void> unmount(Custody& mount_point);
ErrorOr<NonnullLockRefPtr<OpenFileDescription>> open(Credentials const&, StringView path, int options, mode_t mode, Custody& base, Optional<UidAndGid> = {});
ErrorOr<NonnullLockRefPtr<OpenFileDescription>> open(Process const&, Credentials const&, StringView path, int options, mode_t mode, Custody& base, Optional<UidAndGid> = {});
ErrorOr<NonnullLockRefPtr<OpenFileDescription>> create(Credentials const&, StringView path, int options, mode_t mode, Custody& parent_custody, Optional<UidAndGid> = {});
ErrorOr<NonnullLockRefPtr<OpenFileDescription>> create(Process const&, Credentials const&, StringView path, int options, mode_t mode, Custody& parent_custody, Optional<UidAndGid> = {});
ErrorOr<void> mkdir(Credentials const&, StringView path, mode_t mode, Custody& base);
ErrorOr<void> link(Credentials const&, StringView old_path, StringView new_path, Custody& base);
ErrorOr<void> unlink(Credentials const&, StringView path, Custody& base);
@ -92,12 +94,15 @@ public:
NonnullRefPtr<Custody> root_custody();
ErrorOr<NonnullRefPtr<Custody>> resolve_path(Credentials const&, StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent = nullptr, int options = 0, int symlink_recursion_level = 0);
ErrorOr<NonnullRefPtr<Custody>> resolve_path(Process const&, Credentials const&, StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent = nullptr, int options = 0, int symlink_recursion_level = 0);
ErrorOr<NonnullRefPtr<Custody>> resolve_path_without_veil(Credentials const&, StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent = nullptr, int options = 0, int symlink_recursion_level = 0);
private:
friend class OpenFileDescription;
UnveilNode const& find_matching_unveiled_path(StringView path);
UnveilNode const& find_matching_unveiled_path(Process const&, StringView path);
ErrorOr<void> validate_path_against_process_veil(Process const&, StringView path, int options);
ErrorOr<void> validate_path_against_process_veil(Process const& process, Custody const& custody, int options);
ErrorOr<void> validate_path_against_process_veil(Custody const& path, int options);
ErrorOr<void> validate_path_against_process_veil(StringView path, int options);

2
Kernel/Process.cpp
View File

@ -709,7 +709,7 @@ ErrorOr<void> Process::dump_perfcore()
LockRefPtr<OpenFileDescription> description;
auto credentials = this->credentials();
for (size_t attempt = 1; attempt <= 10; ++attempt) {
auto description_or_error = VirtualFileSystem::the().open(credentials, perfcore_filename->view(), O_CREAT | O_EXCL, 0400, current_directory(), UidAndGid { 0, 0 });
auto description_or_error = VirtualFileSystem::the().open(*this, credentials, perfcore_filename->view(), O_CREAT | O_EXCL, 0400, current_directory(), UidAndGid { 0, 0 });
if (!description_or_error.is_error()) {
description = description_or_error.release_value();
break;