libelf: Check header exists in elf_strptr

We already checked the header actually existed for ELFCLASS64 but not
for the ELFCLASS32 case. It is very unlikely it is at this point in the
code, but theoretically it could happen.

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

diff --git a/libelf/ChangeLog b/libelf/ChangeLog
index aee1fff..db3eed0 100644 (file)
--- a/libelf/ChangeLog
+++ b/libelf/ChangeLog
@@ -1,5 +1,9 @@
 2020-11-01  Mark Wielaard  <mark@klomp.org>
 
+       * elf_strptr.c (elf_strptr): Check shdr is not NULL.
+
+2020-11-01  Mark Wielaard  <mark@klomp.org>
+
        * elf_getphdrnum.c (__elf_getphdrnum_rdlock): Set *dst to zero on
        error.
 

diff --git a/libelf/elf_strptr.c b/libelf/elf_strptr.c
index c727170..76f2caf 100644 (file)
--- a/libelf/elf_strptr.c
+++ b/libelf/elf_strptr.c
@@ -119,7 +119,7 @@ elf_strptr (Elf *elf, size_t idx, size_t offset)
   if (elf->class == ELFCLASS32)
     {
       Elf32_Shdr *shdr = strscn->shdr.e32 ?: __elf32_getshdr_rdlock (strscn);
-      if (unlikely (shdr->sh_type != SHT_STRTAB))
+      if (unlikely (shdr == NULL || shdr->sh_type != SHT_STRTAB))
        {
          /* This is no string section.  */
          __libelf_seterrno (ELF_E_INVALID_SECTION);