Commit `4d77ef25f9`

Jakub Konka <kubkon@jakubkonka.com>

2022-04-14 15:16:51

elf: check symtab section headers size when writing globals

Without this, it may happen we write the globals without extending the symtab section header's size. This can potentially lead to clobbering some data in the file, or simply omitting the globals from the symtab when displaying with support tooling such as `readelf`.

master

1 parent 7a00227

Changed files (1)

src

link

Elf.zig

@@ -2799,6 +2799,22 @@ fn writeAllGlobalSymbols(self: *Elf) !void {
         .p32 => @sizeOf(elf.Elf32_Sym),
         .p64 => @sizeOf(elf.Elf64_Sym),
     };
+    const sym_align: u16 = switch (self.ptr_width) {
+        .p32 => @alignOf(elf.Elf32_Sym),
+        .p64 => @alignOf(elf.Elf64_Sym),
+    };
+    const needed_size = (self.local_symbols.items.len + self.global_symbols.items.len) * sym_size;
+    if (needed_size > self.allocatedSize(syms_sect.sh_offset)) {
+        // Move all the symbols to a new file location.
+        const new_offset = self.findFreeSpace(needed_size, sym_align);
+        const existing_size = @as(u64, syms_sect.sh_info) * sym_size;
+        const amt = try self.base.file.?.copyRangeAll(syms_sect.sh_offset, self.base.file.?, new_offset, existing_size);
+        if (amt != existing_size) return error.InputOutput;
+        syms_sect.sh_offset = new_offset;
+    }
+    syms_sect.sh_size = needed_size; // anticipating adding the global symbols later
+    self.shdr_table_dirty = true; // TODO look into only writing one section
+
     const foreign_endian = self.base.options.target.cpu.arch.endian() != builtin.cpu.arch.endian();
     const global_syms_off = syms_sect.sh_offset + self.local_symbols.items.len * sym_size;
     switch (self.ptr_width) {

Commit 4d77ef25f9

Commit `4d77ef25f9`