Kernel: Only load program headers of interpreter if its present

I was loading program headers of both executable and interpreter but
that is incorrect. The interpreter will itself load the program headers
of the executable.

kernel/kernel/Process.cpp

@@ -519,8 +519,8 @@ namespace Kernel
 			{
 				VirtualFileSystem::File file;
 				TRY(file.canonical_path.append("<self>"));
-				file.inode = m_loadable_elf->inode();
+				file.inode = m_loadable_elf->executable();
-				m_userspace_info.file_fd = TRY(m_open_file_descriptors.open(BAN::move(file), O_EXEC));
+				m_userspace_info.file_fd = TRY(m_open_file_descriptors.open(BAN::move(file), O_RDONLY));
 			}
 
 			for (size_t i = 0; i < sizeof(m_signal_handlers) / sizeof(*m_signal_handlers); i++)

userspace/libraries/LibELF/LibELF/LoadableELF.cpp

@@ -26,10 +26,10 @@ namespace LibELF
 
 	LoadableELF::~LoadableELF()
 	{
-		const auto cleanup_program_headers =
+		if (!m_is_loaded)
-			[&](BAN::Span<const ElfNativeProgramHeader> headers)
+			return;
-			{
+
-				for (const auto& header : headers)
+		for (const auto& header : m_program_headers)
 		{
 			ASSERT(header.p_type == PT_LOAD);
 
@@ -40,12 +40,6 @@ namespace LibELF
 					Heap::get().release_page(paddr);
 			m_page_table.unmap_range(vaddr, pages * PAGE_SIZE);
 		}
-			};
-
-		if (!m_is_loaded)
-			return;
-		cleanup_program_headers(m_executable.program_headers.span());
-		cleanup_program_headers(m_interpreter.program_headers.span());
 	}
 
 	static BAN::ErrorOr<ElfNativeFileHeader> read_and_validate_file_header(BAN::RefPtr<Inode> inode)
@@ -166,30 +160,26 @@ namespace LibELF
 		}
 
 		return LoadResult {
-			.elf_file = {
 			.inode = inode,
+			.interp = interp,
 			.file_header = file_header,
-				.program_headers = BAN::move(program_headers),
+			.program_headers = BAN::move(program_headers)
-				.dynamic_base = 0
-			},
-			.interp = interp
 		};
 	}
 
-	bool LoadableELF::does_executable_and_interpreter_overlap() const
+	static bool do_program_headers_overlap(BAN::Span<const ElfNativeProgramHeader> pheaders1, BAN::Span<const ElfNativeProgramHeader> pheaders2, vaddr_t base2)
 	{
-		ASSERT(m_executable.inode);
+		for (const auto& pheader1 : pheaders1)
-		ASSERT(m_interpreter.inode);
+		{
+			for (const auto& pheader2 : pheaders2)
+			{
+				const vaddr_t s1 =  pheader1.p_vaddr & PAGE_ADDR_MASK;
+				const vaddr_t e1 = (pheader1.p_vaddr + pheader1.p_memsz + PAGE_SIZE - 1) & PAGE_ADDR_MASK;
 
-		for (const auto& epheader : m_executable.program_headers)
+				const vaddr_t s2 =  pheader2.p_vaddr & PAGE_ADDR_MASK;
-		{
+				const vaddr_t e2 = (pheader2.p_vaddr + pheader2.p_memsz + PAGE_SIZE - 1) & PAGE_ADDR_MASK;
-			for (const auto& ipheader : m_interpreter.program_headers)
+
-			{
+				if (s1 < e2 + base2 && s2 + base2 < e1)
-				const vaddr_t e1 =  epheader.p_vaddr & PAGE_ADDR_MASK;
-				const vaddr_t i1 =  ipheader.p_vaddr & PAGE_ADDR_MASK;
-				const vaddr_t e2 = (epheader.p_vaddr + epheader.p_memsz + PAGE_SIZE - 1) & PAGE_ADDR_MASK;
-				const vaddr_t i2 = (ipheader.p_vaddr + ipheader.p_memsz + PAGE_SIZE - 1) & PAGE_ADDR_MASK;
-				if (e1 < i2 && i1 < e2)
 					return true;
 			}
 		}
@@ -199,74 +189,95 @@ namespace LibELF
 
 	BAN::ErrorOr<void> LoadableELF::initialize(const Credentials& credentials, BAN::RefPtr<Inode> inode)
 	{
+		const auto generate_random_dynamic_base =
+			[]() -> vaddr_t
+			{
+				// 1 MiB -> 2 GiB + 1 MiB
+				return (Random::get_u32() & 0x7FFFF000) + 0x100000;
+			};
+
+
 		auto executable_load_result = TRY(load_elf_file(credentials, inode));
-		m_executable = executable_load_result.elf_file;
 
-		if (m_executable.file_header.e_type == ET_DYN)
+		m_executable = executable_load_result.inode;
+		m_interpreter = executable_load_result.interp;
+
+		vaddr_t dynamic_base = 0;
+
+		if (m_interpreter)
 		{
-			m_executable.dynamic_base = (Random::get_u32() & 0x7FFFF000) + 0x100000;
+			auto interp_load_result = TRY(load_elf_file(credentials, m_interpreter));
-			m_executable.file_header.e_entry += m_executable.dynamic_base;
-			for (auto& program_header : m_executable.program_headers)
-				program_header.p_vaddr += m_executable.dynamic_base;
-		}
-
-		if (executable_load_result.interp)
-		{
-			auto interp_load_result = TRY(load_elf_file(credentials, executable_load_result.interp));
-			m_interpreter = interp_load_result.elf_file;
-
 			if (interp_load_result.interp)
 			{
-				dwarnln("Executable has specified interpreter for its interpreter");
+				dwarnln("ELF interpreter has an interpreter");
 				return BAN::Error::from_errno(EINVAL);
 			}
 
-			if (m_interpreter.file_header.e_type == ET_DYN)
+			if (executable_load_result.file_header.e_type == ET_EXEC)
+			{
+				if (interp_load_result.file_header.e_type == ET_EXEC)
+				{
+					const bool has_overlap = do_program_headers_overlap(
+						executable_load_result.program_headers.span(),
+						interp_load_result.program_headers.span(),
+						0
+					);
+
+					if (has_overlap)
+					{
+						dwarnln("Executable and interpreter LOAD segments overlap");
+						return BAN::Error::from_errno(EINVAL);
+					}
+				}
+				else
 				{
 					for (int attempt = 0; attempt < 100; attempt++)
 					{
-					const vaddr_t dynamic_base = (Random::get_u32() & 0x3FFFF000) + 0x40000000;
+						const vaddr_t test_dynamic_base = generate_random_dynamic_base();
-					for (auto& program_header : m_interpreter.program_headers)
+						const bool has_overlap = do_program_headers_overlap(
-						program_header.p_vaddr += dynamic_base;
+							executable_load_result.program_headers.span(),
-					if (does_executable_and_interpreter_overlap())
+							interp_load_result.program_headers.span(),
-					{
+							test_dynamic_base
-						for (auto& program_header : m_interpreter.program_headers)
+						);
-							program_header.p_vaddr -= dynamic_base;
+						if (has_overlap)
 							continue;
-					}
+						dynamic_base = test_dynamic_base;
-					m_interpreter.dynamic_base = dynamic_base;
-					m_interpreter.file_header.e_entry += dynamic_base;
 						break;
 					}
-			}
 
-			const bool can_load_interpreter = (m_interpreter.file_header.e_type == ET_DYN)
+					if (dynamic_base == 0)
-				? (m_interpreter.dynamic_base != 0)
-				: !does_executable_and_interpreter_overlap();
-
-			if (!can_load_interpreter)
 					{
 						dwarnln("Could not find space to load interpreter");
 						return BAN::Error::from_errno(EINVAL);
 					}
 				}
+			}
+
+			m_file_header = interp_load_result.file_header;
+			m_program_headers = BAN::move(interp_load_result.program_headers);
+		}
+		else
+		{
+			m_file_header = executable_load_result.file_header;
+			m_program_headers = BAN::move(executable_load_result.program_headers);
+		}
+
+		if (m_file_header.e_type == ET_DYN && dynamic_base == 0)
+			dynamic_base = generate_random_dynamic_base();
+
+		if (dynamic_base)
+		{
+			m_file_header.e_entry += dynamic_base;
+			for (auto& program_header : m_program_headers)
+				program_header.p_vaddr += dynamic_base;
+		}
 
 		return {};
 	}
 
-	vaddr_t LoadableELF::entry_point() const
-	{
-		if (m_interpreter.inode)
-			return m_interpreter.file_header.e_entry;
-		return m_executable.file_header.e_entry;
-	}
-
 	bool LoadableELF::contains(vaddr_t address) const
 	{
-		for (const auto& program_header : m_executable.program_headers)
+		for (const auto& program_header : m_program_headers)
-			if (program_header.p_vaddr <= address && address < program_header.p_vaddr + program_header.p_memsz)
-				return true;
-		for (const auto& program_header : m_interpreter.program_headers)
 			if (program_header.p_vaddr <= address && address < program_header.p_vaddr + program_header.p_memsz)
 				return true;
 		return false;
@@ -274,10 +285,7 @@ namespace LibELF
 
 	bool LoadableELF::is_address_space_free() const
 	{
-		const auto are_program_headers_free =
+		for (const auto& program_header : m_program_headers)
-			[&](BAN::Span<const ElfNativeProgramHeader> program_headers) -> bool
-			{
-				for (const auto& program_header : program_headers)
 		{
 			ASSERT(program_header.p_type == PT_LOAD);
 			const vaddr_t page_vaddr = program_header.p_vaddr & PAGE_ADDR_MASK;
@@ -286,20 +294,11 @@ namespace LibELF
 				return false;
 		}
 		return true;
-			};
-		if (!are_program_headers_free(m_executable.program_headers.span()))
-			return false;
-		if (!are_program_headers_free(m_interpreter.program_headers.span()))
-			return false;
-		return true;
 	}
 
 	void LoadableELF::reserve_address_space()
 	{
-		const auto reserve_program_headers =
+		for (const auto& program_header : m_program_headers)
-			[&](BAN::Span<const ElfNativeProgramHeader> program_headers)
-			{
-				for (const auto& program_header : program_headers)
 		{
 			ASSERT(program_header.p_type == PT_LOAD);
 			const vaddr_t page_vaddr = program_header.p_vaddr & PAGE_ADDR_MASK;
@@ -308,29 +307,24 @@ namespace LibELF
 				ASSERT_NOT_REACHED();
 			m_virtual_page_count += pages;
 		}
-			};
-		reserve_program_headers(m_executable.program_headers.span());
-		reserve_program_headers(m_interpreter.program_headers.span());
 		m_is_loaded = true;
 	}
 
 	void LoadableELF::update_suid_sgid(Kernel::Credentials& credentials)
 	{
-		auto inode = m_executable.inode;
+		if (m_executable->mode().mode & +Inode::Mode::ISUID)
-		ASSERT(inode);
+			credentials.set_euid(m_executable->uid());
-
+		if (m_executable->mode().mode & +Inode::Mode::ISGID)
-		if (inode->mode().mode & +Inode::Mode::ISUID)
+			credentials.set_egid(m_executable->gid());
-			credentials.set_euid(inode->uid());
-		if (inode->mode().mode & +Inode::Mode::ISGID)
-			credentials.set_egid(inode->gid());
 	}
 
 	BAN::ErrorOr<void> LoadableELF::load_page_to_memory(vaddr_t address)
 	{
-		const auto load_page_from_program_header =
+		auto inode = has_interpreter() ? m_interpreter : m_executable;
-			[&](BAN::RefPtr<Inode> inode, BAN::Span<const ElfNativeProgramHeader> program_headers) -> BAN::ErrorOr<bool>
+
-			{
+		// FIXME: use MemoryBackedRegion/FileBackedRegion instead of manually mapping and allocating pages
-				for (const auto& program_header : program_headers)
+
+		for (const auto& program_header : m_program_headers)
 		{
 			ASSERT(program_header.p_type == PT_LOAD);
 			if (!(program_header.p_vaddr <= address && address < program_header.p_vaddr + program_header.p_memsz))
@@ -370,16 +364,9 @@ namespace LibELF
 			// Map page with the correct flags
 			m_page_table.map_page_at(paddr, vaddr, flags);
 
-					return true;
+			return {};
 		}
 
-				return false;
-			};
-
-		if (TRY(load_page_from_program_header(m_executable.inode, m_executable.program_headers.span())))
-			return {};
-		if (TRY(load_page_from_program_header(m_interpreter.inode, m_interpreter.program_headers.span())))
-			return {};
 		ASSERT_NOT_REACHED();
 	}
 
@@ -387,27 +374,16 @@ namespace LibELF
 	{
 		auto elf = TRY(BAN::UniqPtr<LoadableELF>::create(new_page_table));
 
-		const auto clone_loadable_file =
+		elf->m_executable = m_executable;
-			[](const LoadableElfFile& source, LoadableElfFile& destination) -> BAN::ErrorOr<void>
+		elf->m_interpreter = m_interpreter;
-			{
+		elf->m_file_header = m_file_header;
-				if (!source.inode)
+		TRY(elf->m_program_headers.reserve(m_program_headers.size()));
-					return {};
+		for (const auto& program_header : m_program_headers)
+			MUST(elf->m_program_headers.emplace_back(program_header));
 
-				destination.inode = source.inode;
+		elf->reserve_address_space();
-				destination.file_header = source.file_header;
-				destination.dynamic_base = source.dynamic_base;
 
-				TRY(destination.program_headers.reserve(source.program_headers.size()));
+		for (const auto& program_header : m_program_headers)
-				for (const auto& program_header : source.program_headers)
-					MUST(destination.program_headers.emplace_back(program_header));
-
-				return {};
-			};
-
-		const auto map_loadable_file =
-			[&](BAN::Span<const ElfNativeProgramHeader> program_headers) -> BAN::ErrorOr<void>
-			{
-				for (const auto& program_header : program_headers)
 		{
 			ASSERT(program_header.p_type == PT_LOAD);
 			if (!(program_header.p_flags & LibELF::PF_W))
@@ -439,16 +415,6 @@ namespace LibELF
 				elf->m_physical_page_count++;
 			}
 		}
-				return {};
-			};
-
-		TRY(clone_loadable_file(m_executable, elf->m_executable));
-		TRY(clone_loadable_file(m_interpreter, elf->m_interpreter));
-
-		elf->reserve_address_space();
-
-		TRY(map_loadable_file(elf->m_executable.program_headers.span()));
-		TRY(map_loadable_file(elf->m_interpreter.program_headers.span()));
 
 		return elf;
 	}

userspace/libraries/LibELF/include/LibELF/LoadableELF.h

@@ -25,10 +25,10 @@ namespace LibELF
 		static BAN::ErrorOr<BAN::UniqPtr<LoadableELF>> load_from_inode(Kernel::PageTable&, const Kernel::Credentials&, BAN::RefPtr<Kernel::Inode>);
 		~LoadableELF();
 
-		Kernel::vaddr_t entry_point() const;
+		Kernel::vaddr_t entry_point() const { return m_file_header.e_entry; }
 
-		bool has_interpreter() const { return !!m_interpreter.inode; }
+		bool has_interpreter() const { return !!m_interpreter; }
-		BAN::RefPtr<Kernel::Inode> inode() { return m_executable.inode; }
+		BAN::RefPtr<Kernel::Inode> executable() { return m_executable; }
 
 		bool contains(Kernel::vaddr_t address) const;
 		bool is_address_space_free() const;
@@ -44,30 +44,25 @@ namespace LibELF
 		size_t physical_page_count() const { return m_physical_page_count; }
 
 	private:
-		struct LoadableElfFile
-		{
-			BAN::RefPtr<Kernel::Inode> inode;
-			ElfNativeFileHeader file_header;
-			BAN::Vector<ElfNativeProgramHeader>	program_headers;
-			Kernel::vaddr_t dynamic_base;
-		};
-
 		struct LoadResult
 		{
-			LoadableElfFile elf_file;
+			BAN::RefPtr<Kernel::Inode> inode;
 			BAN::RefPtr<Kernel::Inode> interp;
+			ElfNativeFileHeader file_header;
+			BAN::Vector<ElfNativeProgramHeader>	program_headers;
 		};
 
 	private:
 		LoadableELF(Kernel::PageTable&);
 		BAN::ErrorOr<void> initialize(const Kernel::Credentials&, BAN::RefPtr<Kernel::Inode>);
-
-		bool does_executable_and_interpreter_overlap() const;
 		BAN::ErrorOr<LoadResult> load_elf_file(const Kernel::Credentials&, BAN::RefPtr<Kernel::Inode>) const;
 
 	private:
-		LoadableElfFile    m_executable;
+		BAN::RefPtr<Kernel::Inode>          m_executable;
-		LoadableElfFile    m_interpreter;
+		BAN::RefPtr<Kernel::Inode>          m_interpreter;
+		ElfNativeFileHeader                 m_file_header;
+		BAN::Vector<ElfNativeProgramHeader>	m_program_headers;
+
 		Kernel::PageTable& m_page_table;
 		size_t             m_virtual_page_count  { 0 };
 		size_t             m_physical_page_count { 0 };