[PATCH] libdw: Make sure dirarray is always properly freed in dwarf_getsrclines.

[Mark Wielaard <mark@klomp.org>]

If there were more than 256 directories in the table and there was
illegal DWARF before we read them all, then we might not free the
dirarray (or the wrong one). Fix by defining the dirarray early
(before the first data sanity check) and making sure it is not
(still) equal to dirstack before freeing.

Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 libdw/ChangeLog           |  6 ++++++
 libdw/dwarf_getsrclines.c | 21 ++++++++++++---------
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index b9f177d..f0ce901 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,5 +1,11 @@
 2018-06-05  Mark Wielaard  <mark@klomp.org>
 
+	* dwarf_getsrclines.c (read_srclines): Define dirarray early and
+	check whether or not it is equal to dirstack on exit/out before
+	cleanup.
+
+2018-06-05  Mark Wielaard  <mark@klomp.org>
+
 	* dwarf_getalt.c (find_debug_altlink): id_path array should be 2
 	larger to contain MAX_BUILD_ID_BYTES.
 
diff --git a/libdw/dwarf_getsrclines.c b/libdw/dwarf_getsrclines.c
index 790d4e4..0c2efaa 100644
--- a/libdw/dwarf_getsrclines.c
+++ b/libdw/dwarf_getsrclines.c
@@ -182,6 +182,17 @@ read_srclines (Dwarf *dbg,
       .discriminator = 0
     };
 
+  /* The dirs normally go on the stack, but if there are too many
+     we alloc them all.  Set up stack storage early, so we can check on
+     error if we need to free them or not.  */
+  struct dirlist
+  {
+    const char *dir;
+    size_t len;
+  };
+  struct dirlist dirstack[MAX_STACK_DIRS];
+  struct dirlist *dirarray = dirstack;
+
   if (unlikely (linep + 4 > lineendp))
     {
     invalid_data:
@@ -347,14 +358,6 @@ read_srclines (Dwarf *dbg,
 	goto invalid_data;
     }
 
-  struct dirlist
-  {
-    const char *dir;
-    size_t len;
-  };
-  struct dirlist dirstack[MAX_STACK_DIRS];
-  struct dirlist *dirarray = dirstack;
-
   /* Arrange the list in array form.  */
   ndirlist = ndirs;
   if (ndirlist >= MAX_STACK_DIRS)
@@ -1051,7 +1054,7 @@ read_srclines (Dwarf *dbg,
       free (state.linelist);
       state.linelist = ll;
     }
-  if (ndirlist >= MAX_STACK_DIRS)
+  if (dirarray != dirstack)
     free (dirarray);
   for (size_t i = MAX_STACK_FILES; i < nfilelist; i++)
     {
-- 
1.8.3.1