From: Mark Wielaard <mark@klomp.org>
Date: Mon, 15 Sep 2025 21:58:08 +0000 (+0200)
Subject: libelf: check ehdr isn't NULL before calling default_ehdr
X-Git-Tag: elfutils-0.194~17
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=13153e98ee4f4b4ad2c73c2a747b6c2db984e029;p=thirdparty%2Felfutils.git

libelf: check ehdr isn't NULL before calling default_ehdr

default_ehdr assumes the passed ehdr pointer is not NULL and can be
directly dereferenced. But getehdr can return NULL. So explicitly
check.

	* libelf/elf32_updatenull.c (updatenull_wrlock): Check ehdr is
        not NULL.

https://sourceware.org/bugzilla/show_bug.cgi?id=33433

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

diff --git a/libelf/elf32_updatenull.c b/libelf/elf32_updatenull.c
index 3594e8ba..74c27fda 100644
--- a/libelf/elf32_updatenull.c
+++ b/libelf/elf32_updatenull.c
@@ -135,7 +135,8 @@ __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
   ehdr = __elfw2(LIBELFBITS,getehdr_wrlock) (elf);
 
   /* Set the default values.  */
-  if (ELFW(default_ehdr,LIBELFBITS) (elf, ehdr, shnum, change_bop) != 0)
+  if (ehdr == NULL
+      || ELFW(default_ehdr,LIBELFBITS) (elf, ehdr, shnum, change_bop) != 0)
     return -1;
 
   /* At least the ELF header is there.  */