Avoid stack overflow in native symbolification

If looking up debug info by build id returns a file with MiniDebugInfo
(the `.gnu_debugdata` section), libbacktrace will infinitely recurse,
leading to a stack overflow unless the limit on the maximum number of
open file descriptors is reached before the stack can overflow.

Work around this by ignoring the MiniDebugInfo if we've already
successfully loaded the debug info by its build id.

Signed-off-by: Matt Wozniski <mwozniski@bloomberg.net>

news/639.bugfix.rst

@@ -0,0 +1 @@
+Fix a bug that could in rare circumstances result in a stack overflow while processing native mode stacks.

src/vendor/libbacktrace/elf.c

@@ -6876,7 +6876,8 @@ elf_add (struct backtrace_state *state, const char *filename, int descriptor,
 	    }
 	}
 
-      if (!gnu_debugdata_view_valid
+      if (!debuginfo
+	  && !gnu_debugdata_view_valid
 	  && strcmp (name, ".gnu_debugdata") == 0)
 	{
 	  if (!elf_get_view (state, descriptor, memory, memory_size,

src/vendor/libbacktrace_4ead348bb45f753121ca0bd44170ff8352d4c514_debuginfod_patch.diff

@@ -180,7 +180,7 @@ index 0000000..78f4d8d
 +
 +#endif /* _DEBUGINFOD_CLIENT_H */
 diff --git a/elf.c b/elf.c
-index 107e26c..3d2b75f 100644
+index 107e26c..e62668b 100644
 --- a/elf.c
 +++ b/elf.c
 @@ -38,6 +38,7 @@ POSSIBILITY OF SUCH DAMAGE.  */
@@ -239,7 +239,17 @@ index 107e26c..3d2b75f 100644
  /* Open a separate debug info file, using the build ID to find it.
     Returns an open file descriptor, or -1.
 
-@@ -6946,6 +6981,14 @@ elf_add (struct backtrace_state *state, const char *filename, int descriptor,
+@@ -6841,7 +6876,8 @@ elf_add (struct backtrace_state *state, const char *filename, int descriptor,
+ 	    }
+ 	}
+
+-      if (!gnu_debugdata_view_valid
++      if (!debuginfo
++	  && !gnu_debugdata_view_valid
+ 	  && strcmp (name, ".gnu_debugdata") == 0)
+ 	{
+ 	  if (!elf_get_view (state, descriptor, memory, memory_size,
+@@ -6946,6 +6982,14 @@ elf_add (struct backtrace_state *state, const char *filename, int descriptor,
 
        d = elf_open_debugfile_by_buildid (state, buildid_data, buildid_size,
  					 error_callback, data);
@@ -254,7 +264,7 @@ index 107e26c..3d2b75f 100644
        if (d >= 0)
  	{
  	  int ret;
-@@ -7421,7 +7464,28 @@ backtrace_initialize (struct backtrace_state *state, const char *filename,
+@@ -7421,7 +7465,28 @@ backtrace_initialize (struct backtrace_state *state, const char *filename,
    pd.exe_filename = filename;
    pd.exe_descriptor = ret < 0 ? descriptor : -1;