libelf: Allow updating phdrs for any e_type.

elf[32|64]_updatenull would sanity check the e_type before allowing to
update the phdrs. This prevents creating an ET_REL file with phdrs. It
also prevents creating any vendor specific ELF file having phdrs. We
only check this when updating/writing out the file. But we would just
read such files. Don't prevent people from creating unexpected ELF files.
elflint will warn for such files.

While writing a new testcase for this another bug was found that
prevented updating a just created phdr because elf_getphdrnum would
sanity check the phdr offset in the file (which doesn't exist yet).
Fix that by only doing such a sanity check if the phdrs haven't been
read in or created yet.

This second bug should have been found by the existing elfshphehdr
test, but that test contained a typo checking elf_getphdrnum.
It tested that the called failed when there were no phdrs, but then
elf_getphdrnum should simply succeed and return zero.

https://bugzilla.redhat.com/show_bug.cgi?id=1352232

Signed-off-by: Mark Wielaard <[email protected]>

1 files changed, 31 insertions, 27 deletions

diff --git a/libelf/elf_getphdrnum.c b/libelf/elf_getphdrnum.c
index 061183bb..f91cba98 100644
--- a/libelf/elf_getphdrnum.c
+++ b/libelf/elf_getphdrnum.c
@@ -1,5 +1,5 @@
 /* Return number of program headers in the ELF file.
-   Copyright (C) 2010, 2014, 2015 Red Hat, Inc.
+   Copyright (C) 2010, 2014, 2015, 2016 Red Hat, Inc.
    This file is part of elfutils.
 
    This file is free software; you can redistribute it and/or modify
@@ -84,35 +84,39 @@ __elf_getphdrnum_chk_rdlock (Elf *elf, size_t *dst)
 {
   int result = __elf_getphdrnum_rdlock (elf, dst);
 
-  /* Do some sanity checking to make sure phnum and phoff are consistent.  */
-  Elf64_Off off = (elf->class == ELFCLASS32
-		   ? elf->state.elf32.ehdr->e_phoff
-		   : elf->state.elf64.ehdr->e_phoff);
-  if (unlikely (off == 0))
+  /* If the phdrs haven't been created or read in yet then do some
+     sanity checking to make sure phnum and phoff are consistent.  */
+  if (elf->state.elf.phdr == NULL)
     {
-      *dst = 0;
-      return result;
+      Elf64_Off off = (elf->class == ELFCLASS32
+		       ? elf->state.elf32.ehdr->e_phoff
+		       : elf->state.elf64.ehdr->e_phoff);
+      if (unlikely (off == 0))
+	{
+	  *dst = 0;
+	  return result;
+	}
+
+      if (unlikely (off >= elf->maximum_size))
+	{
+	  __libelf_seterrno (ELF_E_INVALID_DATA);
+	  return -1;
+	}
+
+      /* Check for too many sections.  */
+      size_t phdr_size = (elf->class == ELFCLASS32
+			  ? sizeof (Elf32_Phdr) : sizeof (Elf64_Phdr));
+      if (unlikely (*dst > SIZE_MAX / phdr_size))
+	{
+	  __libelf_seterrno (ELF_E_INVALID_DATA);
+	  return -1;
+	}
+
+      /* Truncated file?  Don't return more than can be indexed.  */
+      if (unlikely (elf->maximum_size - off < *dst * phdr_size))
+	*dst = (elf->maximum_size - off) / phdr_size;
     }
 
-  if (unlikely (off >= elf->maximum_size))
-    {
-      __libelf_seterrno (ELF_E_INVALID_DATA);
-      return -1;
-    }
-
-  /* Check for too many sections.  */
-  size_t phdr_size = (elf->class == ELFCLASS32
-		      ? sizeof (Elf32_Phdr) : sizeof (Elf64_Phdr));
-  if (unlikely (*dst > SIZE_MAX / phdr_size))
-    {
-      __libelf_seterrno (ELF_E_INVALID_DATA);
-      return -1;
-    }
-
-  /* Truncated file?  Don't return more than can be indexed.  */
-  if (unlikely (elf->maximum_size - off < *dst * phdr_size))
-    *dst = (elf->maximum_size - off) / phdr_size;
-
   return result;
 }