From: Mark Wielaard <mark@klomp.org>
Date: Tue, 14 Nov 2023 20:34:50 +0000 (+0100)
Subject: libelf: Fix elf_begin.c build on 32bit arches.
X-Git-Tag: elfutils-0.191~41
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f84f1cd7e296bf223cb45b5469978d4bea82cec0;p=thirdparty%2Felfutils.git

libelf: Fix elf_begin.c build on 32bit arches.

On 32bit architectures gcc produces an error:

elf_begin.c: In function ‘file_read_elf’:
elf_begin.c:495:30: error: cast to pointer from integer of different
size [-Werror=int-to-pointer-cast]
      elf->state.elf64.shdr = (Elf64_Shdr *) (ehdr + e_shoff);
                              ^

This is because we are adding an uintptr to an Elf64_Off which
promotes the result to a 64bit value. Fix this by casting the
e_shoff to an ptrdiff_t. This is fine since the mmap of the file
would have failed if it didn't fit in the 32bit address space
and we check that e_shoff fits inside the image.

	* libelf/elf_begin.c (file_read_elf): Cast e_shoff to ptrdiff_t
	before adding to ehdr.

Suggested-by: Paul Pluzhnikov <ppluzhnikov@google.com>
Signed-off-by: Mark Wielaard <mark@klomp.org>
---

diff --git a/libelf/elf_begin.c b/libelf/elf_begin.c
index 9f8196b6d..dcaad8eea 100644
--- a/libelf/elf_begin.c
+++ b/libelf/elf_begin.c
@@ -492,7 +492,7 @@ file_read_elf (int fildes, void *map_address, unsigned char *e_ident,
 	    goto free_and_out;
 
 	  if (scncnt > 0)
-	    elf->state.elf64.shdr = (Elf64_Shdr *) (ehdr + e_shoff);
+	    elf->state.elf64.shdr = (Elf64_Shdr *) (ehdr + (ptrdiff_t) e_shoff);
 
 	  for (size_t cnt = 0; cnt < scncnt; ++cnt)
 	    {