findtextrel: Check that sh_entsize isn't zero.

A bogus ELF file could have sh_entsize as zero. Don't divide by zero,
but just assume there are no entries in the section.

https://sourceware.org/bugzilla/show_bug.cgi?id=23755

Signed-off-by: Mark Wielaard <mark@klomp.org>

diff --git a/src/ChangeLog b/src/ChangeLog
index 680291b..d057669 100644 (file)
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,7 @@
+2018-10-14  Mark Wielaard  <mark@klomp.org>
+
+       * findtextrel.c (process_file): Check that sh_entsize is not zero.
+
 2018-09-13  Mark Wielaard  <mark@klomp.org>
 
        * readelf.c (print_debug_macro_section): Use elf_getdata. Print

diff --git a/src/findtextrel.c b/src/findtextrel.c
index 4973159..f48752e 100644 (file)
--- a/src/findtextrel.c
+++ b/src/findtextrel.c
@@ -1,5 +1,5 @@
 /* Locate source files or functions which caused text relocations.
-   Copyright (C) 2005-2010, 2012, 2014 Red Hat, Inc.
+   Copyright (C) 2005-2010, 2012, 2014, 2018 Red Hat, Inc.
    This file is part of elfutils.
    Written by Ulrich Drepper <drepper@redhat.com>, 2005.
 
@@ -263,9 +263,10 @@ process_file (const char *fname, bool more_than_one)
              seen_dynamic = true;
 
              Elf_Data *data = elf_getdata (scn, NULL);
+             size_t entries = (shdr->sh_entsize == 0
+                               ? 0 : shdr->sh_size / shdr->sh_entsize);
 
-             for (size_t cnt = 0; cnt < shdr->sh_size / shdr->sh_entsize;
-                  ++cnt)
+             for (size_t cnt = 0; cnt < entries; ++cnt)
                {
                  GElf_Dyn dynmem;
                  GElf_Dyn *dyn;
@@ -413,10 +414,11 @@ cannot get symbol table section %zu in '%s': %s"),
          if (shdr->sh_type == SHT_REL)
            {
              Elf_Data *data = elf_getdata (scn, NULL);
+             size_t entries = (shdr->sh_entsize == 0
+                               ? 0 : shdr->sh_size / shdr->sh_entsize);
 
              for (int cnt = 0;
-                  (size_t) cnt < shdr->sh_size / shdr->sh_entsize;
-                  ++cnt)
+                  (size_t) cnt < entries; ++cnt)
                {
                  GElf_Rel rel_mem;
                  GElf_Rel *rel = gelf_getrel (data, cnt, &rel_mem);
@@ -436,10 +438,10 @@ cannot get relocation at index %d in section %zu in '%s': %s"),
          else if (shdr->sh_type == SHT_RELA)
            {
              Elf_Data *data = elf_getdata (scn, NULL);
+             size_t entries = (shdr->sh_entsize == 0
+                               ? 0 : shdr->sh_size / shdr->sh_entsize);
 
-             for (int cnt = 0;
-                  (size_t) cnt < shdr->sh_size / shdr->sh_entsize;
-                  ++cnt)
+             for (int cnt = 0; (size_t) cnt < entries; ++cnt)
                {
                  GElf_Rela rela_mem;
                  GElf_Rela *rela = gelf_getrela (data, cnt, &rela_mem);
@@ -531,9 +533,10 @@ check_rel (size_t nsegments, struct segments segments[nsegments],
                int highidx = -1;
                GElf_Sym sym_mem;
                GElf_Sym *sym;
+               size_t entries = (shdr->sh_entsize == 0
+                                 ? 0 : shdr->sh_size / shdr->sh_entsize);
 
-               for (int i = 0; (size_t) i < shdr->sh_size / shdr->sh_entsize;
-                    ++i)
+               for (int i = 0; (size_t) i < entries; ++i)
                  {
                    sym = gelf_getsym (symdata, i, &sym_mem);
                    if (sym == NULL)