[PATCH] libelf: Check header exists in elf_strptr

[PATCH] libelf: Check header exists in elf_strptr

[Mark Wielaard]

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>
---
 libelf/ChangeLog    | 4 ++++
 libelf/elf_strptr.c | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/libelf/ChangeLog b/libelf/ChangeLog
index aee1ffff..db3eed08 100644
--- a/libelf/ChangeLog
+++ b/libelf/ChangeLog
@@ -1,3 +1,7 @@
+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
diff --git a/libelf/elf_strptr.c b/libelf/elf_strptr.c
index c7271707..76f2caf1 100644
--- 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);
-- 
2.18.4

Re: [PATCH] libelf: Check header exists in elf_strptr

[Mark Wielaard]

On Sun, 2020-11-01 at 19:46 +0100, Mark Wielaard wrote:
> 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.

Pushed.