debug.zig: prevent infinite loops during backtraces

Author: rootbeer

lib/std/debug.zig

@@ -13,6 +13,9 @@ const native_arch = builtin.cpu.arch;
 const native_os = builtin.os.tag;
 const native_endian = native_arch.endian();
 
+/// Maximum distance to walk when iterating through a stack trace.
+pub const max_stack_trace_depth = 50;
+
 pub const MemoryAccessor = @import("debug/MemoryAccessor.zig");
 pub const FixedBufferReader = @import("debug/FixedBufferReader.zig");
 pub const Dwarf = @import("debug/Dwarf.zig");
@@ -458,6 +461,8 @@ pub fn dumpStackTraceFromBase(context: *ThreadContext) void {
             printSourceAtAddress(debug_info, stderr, pc_addr, tty_config) catch return;
         }
 
+        var depth: usize = 0;
+
         while (it.next()) |return_address| {
             printLastUnwindError(&it, debug_info, stderr, tty_config);
 
@@ -468,6 +473,12 @@ pub fn dumpStackTraceFromBase(context: *ThreadContext) void {
             // same behaviour for x86-windows-msvc
             const address = if (return_address == 0) return_address else return_address - 1;
             printSourceAtAddress(debug_info, stderr, address, tty_config) catch return;
+
+            depth += 1;
+            if (depth > max_stack_trace_depth) {
+                stderr.print("Abandoned stack trace after {} frames.\n", .{max_stack_trace_depth}) catch {};
+                break;
+            }
         } else printLastUnwindError(&it, debug_info, stderr, tty_config);
     }
 }
@@ -870,8 +881,14 @@ pub const StackIterator = struct {
         var address = it.next_internal() orelse return null;
 
         if (it.first_address) |first_address| {
+            var depth: usize = 0;
             while (address != first_address) {
                 address = it.next_internal() orelse return null;
+
+                depth += 1;
+                if (depth > max_stack_trace_depth) {
+                    return null;
+                }
             }
             it.first_address = null;
         }
@@ -980,6 +997,8 @@ pub fn writeCurrentStackTrace(
     } else null) orelse StackIterator.init(start_addr, null);
     defer it.deinit();
 
+    var depth: usize = 0;
+
     while (it.next()) |return_address| {
         printLastUnwindError(&it, debug_info, out_stream, tty_config);
 
@@ -990,6 +1009,12 @@ pub fn writeCurrentStackTrace(
         // same behaviour for x86-windows-msvc
         const address = return_address -| 1;
         try printSourceAtAddress(debug_info, out_stream, address, tty_config);
+
+        depth += 1;
+        if (depth > max_stack_trace_depth) {
+            out_stream.print("Abandoned stack trace after {} frames.\n", .{max_stack_trace_depth}) catch {};
+            break;
+        }
     } else printLastUnwindError(&it, debug_info, out_stream, tty_config);
 }