Avoid double-free with debuginfod

PR gdb/29257 points out a possible double free when debuginfod is in
use.  Aside from some ugly warts in the symbol code (an ongoing
issue), the underlying issue in this particular case is that elfread.c
seems to assume that symfile_bfd_open will return NULL on error,
whereas in reality it throws an exception.  As this code isn't
prepared for an exception, bad things result.

This patch fixes the problem by introducing a non-throwing variant of
symfile_bfd_open and using it in the affected places.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29257

1 files changed, 17 insertions, 0 deletions

diff --git a/gdb/symfile.c b/gdb/symfile.c
index bb9981a..8ae2177 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -1769,6 +1769,23 @@ symfile_bfd_open (const char *name)
   return sym_bfd;
 }
 
+/* See symfile.h.  */
+
+gdb_bfd_ref_ptr
+symfile_bfd_open_no_error (const char *name) noexcept
+{
+  try
+    {
+      return symfile_bfd_open (name);
+    }
+  catch (const gdb_exception_error &err)
+    {
+      warning ("%s", err.what ());
+    }
+
+  return nullptr;
+}
+
 /* Return the section index for SECTION_NAME on OBJFILE.  Return -1 if
    the section was not found.  */