libdwfl: Reject very short or really large build-ids.

We cannot handle build-ids less than at least 3 or more than 64 bytes.
Very big build-ids, or very large debug search paths might have blown
up the stack.

Signed-off-by: Mark Wielaard <mjw@redhat.com>

diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index 080825e..f08200e 100644 (file)
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,9 @@
+2015-05-22  Mark Wielaard  <mjw@redhat.com>
+
+       * dwfl_build_id_find_elf.c (__libdwfl_open_by_build_id): Return
+       error when id_len too small or too large. strdup, not strdupa,
+       and free path when done.
+
 2015-05-19  Mark Wielaard  <mjw@redhat.com>
 
        * elf-from-memory.c (elf_from_remote_memory): Don't allocate all

diff --git a/libdwfl/dwfl_build_id_find_elf.c b/libdwfl/dwfl_build_id_find_elf.c
index 062aad1..215782a 100644 (file)
--- a/libdwfl/dwfl_build_id_find_elf.c
+++ b/libdwfl/dwfl_build_id_find_elf.c
@@ -1,5 +1,5 @@
 /* Find an ELF file for a module from its build ID.
-   Copyright (C) 2007-2010, 2014 Red Hat, Inc.
+   Copyright (C) 2007-2010, 2014, 2015 Red Hat, Inc.
    This file is part of elfutils.
 
    This file is free software; you can redistribute it and/or modify
@@ -37,9 +37,20 @@ internal_function
 __libdwfl_open_by_build_id (Dwfl_Module *mod, bool debug, char **file_name,
                            const size_t id_len, const uint8_t *id)
 {
+  /* We don't handle very short or really large build-ids.  We need at
+     at least 3 and allow for up to 64 (normally ids are 20 long).  */
+#define MIN_BUILD_ID_BYTES 3
+#define MAX_BUILD_ID_BYTES 64
+  if (id_len < MIN_BUILD_ID_BYTES || id_len > MAX_BUILD_ID_BYTES)
+    {
+      __libdwfl_seterrno (DWFL_E_WRONG_ID_ELF);
+      return -1;
+    }
+
   /* Search debuginfo_path directories' .build-id/ subdirectories.  */
 
-  char id_name[sizeof "/.build-id/" + 1 + id_len * 2 + sizeof ".debug" - 1];
+  char id_name[sizeof "/.build-id/" + 1 + MAX_BUILD_ID_BYTES * 2
+              + sizeof ".debug" - 1];
   strcpy (id_name, "/.build-id/");
   int n = snprintf (&id_name[sizeof "/.build-id/" - 1],
                    4, "%02" PRIx8 "/", (uint8_t) id[0]);
@@ -55,8 +66,10 @@ __libdwfl_open_by_build_id (Dwfl_Module *mod, bool debug, char **file_name,
            ".debug");
 
   const Dwfl_Callbacks *const cb = mod->dwfl->callbacks;
-  char *path = strdupa ((cb->debuginfo_path ? *cb->debuginfo_path : NULL)
-                       ?: DEFAULT_DEBUGINFO_PATH);
+  char *path = strdup ((cb->debuginfo_path ? *cb->debuginfo_path : NULL)
+                      ?: DEFAULT_DEBUGINFO_PATH);
+  if (path == NULL)
+    return -1;
 
   int fd = -1;
   char *dir;
@@ -90,6 +103,8 @@ __libdwfl_open_by_build_id (Dwfl_Module *mod, bool debug, char **file_name,
       free (name);
     }
 
+  free (path);
+
   /* If we simply found nothing, clear errno.  If we had some other error
      with the file, report that.  Possibly this should treat other errors
      like ENOENT too.  But ignoring all errors could mask some that should