Re: [Rpm-maint] [PATCH] debugedit: Check .debug_str index is valid before use.

[Panu Matilainen]

On 03/09/2018 04:24 PM, Panu Matilainen wrote:
On 03/07/2018 05:25 PM, Mark Wielaard wrote:
debugedit would blindly use an .debug_str index from the .debug_info or
.debug_line sections assuming it would result in a valid string. Which
would crash and burn if the DWARF data was bogus when the string was
used. So check whenever converting an string index into a char pointer
so we can produce a more helpful error message.
https://bugzilla.redhat.com/show_bug.cgi?id=1543912

Signed-off-by: Mark Wielaard <m...@klomp.org>
---
  tools/debugedit.c | 14 ++++++++++++++
  1 file changed, 14 insertions(+)

diff --git a/tools/debugedit.c b/tools/debugedit.c
index 57cd830..6c71cbc 100644
--- a/tools/debugedit.c
+++ b/tools/debugedit.c
@@ -820,6 +820,9 @@ record_file_string_entry_idx (struct strings 
*strings, size_t old_idx)
    struct stridxentry *entry = string_find_new_entry (strings, old_idx);
    if (entry != NULL)
      {
+      if (old_idx >= debug_sections[DEBUG_STR].size)
+    error (1, 0, "Bad string pointer index %zd", old_idx);
+
        Strent *strent;
        const char *old_str = (char *)debug_sections[DEBUG_STR].data + 
old_idx;
        const char *file = skip_dir_prefix (old_str, base_dir);
@@ -870,6 +873,9 @@ record_existing_string_entry_idx (struct strings 
*strings, size_t old_idx)
    struct stridxentry *entry = string_find_new_entry (strings, old_idx);
    if (entry != NULL)
      {
+      if (old_idx >= debug_sections[DEBUG_STR].size)
+    error (1, 0, "Bad string pointer index %zd", old_idx);
+
        const char *str = (char *)debug_sections[DEBUG_STR].data + 
old_idx;
        Strent *strent = strtab_add_len (strings->str_tab,
                         str, strlen (str) + 1);
@@ -1533,6 +1539,10 @@ edit_attributes (DSO *dso, unsigned char *ptr, 
struct abbrev_tag *t, int phase)
          {
            const char *dir;
            size_t idx = do_read_32_relocated (ptr);
+          if (idx >= debug_sections[DEBUG_STR].size)
+            error (1, 0,
+               "%s: Bad string pointer index %zd for comp_dir",
+               dso->filename, idx);
            dir = (char *) debug_sections[DEBUG_STR].data + idx;
            free (comp_dir);
@@ -1558,6 +1568,10 @@ edit_attributes (DSO *dso, unsigned char *ptr, 
struct abbrev_tag *t, int phase)
           case.  */
            char *name;
            size_t idx = do_read_32_relocated (ptr);
+          if (idx >= debug_sections[DEBUG_STR].size)
+        error (1, 0,
+               "%s: Bad string pointer index %zd for unit name",
+               dso->filename, idx);
            name = (char *) debug_sections[DEBUG_STR].data + idx;
            if (*name == '/' && comp_dir == NULL)
          {


I was somewhat tempted to mumble something about putting these 
common-looking checks into a function but ... meh, it's Friday :P

Applied, thanks for the patch!

Actually, this breaks a bunch of testcases:

139: rpmbuild debuginfo subpackages multiple         FAILED 
(rpmbuild.at:973)
140: rpmbuild debuginfo subpackages multiple unique  FAILED 
(rpmbuild.at:1058)
141: rpmbuild debuginfo subpackages multiple unique debugsource FAILED 
(rpmbuild.at:1143)
142: rpmbuild debuginfo subpackages multiple excluded FAILED 
(rpmbuild.at:1231)
143: rpmbuild debuginfo subpackages multiple excluded FAILED 
(rpmbuild.at:1296)

They're all failing with messages like this:

/home/pmatilai/repos/rpm/tests/testing/usr/lib/rpm/debugedit: 
/home/pmatilai/repos/rpm/tests/testing/build/BUILDROOT/test-1.0-1.x86_64/bin/hello2: 
Bad string pointer index 678 for unit name

        - Panu -

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