From 37c59664adcb87bdf3279a5919940785057fe565 Mon Sep 17 00:00:00 2001
From: Alan Modra <amodra@gmail.com>
Date: Fri, 5 Aug 2022 19:40:23 +0930
Subject: asan: ppc64_elf_get_synthetic_symtab heap buffer overflow

Fuzzed input files with sizes of .dynamic not a multiple of dynamic
tag size can result in reading past the end of the buffer with the
current simple checks.  Fix that, and use the same check in other
files that process input object .dynamic section.  (There is no need
for buffer overflow checks in the linker's generated .dynamic
section.)

	* elf32-ppc.c (ppc_elf_get_synthetic_symtab): Sanity check
	.dynamic content buffer reads.
	* elf64-ppc.c (ppc64_elf_get_synthetic_symtab): Likewise.
	* elf64-ia64-vms.c (elf64_vms_link_add_object_symbols): Likewise.
	* elf.c (_bfd_elf_print_private_bfd_data): Simplify .dynamic
	buffer sanity checks.
	* elflink.c (elf_link_add_object_symbols): Avoid possible UB
	subtracting sizeof_dyn from pointer.
---
 bfd/elf.c            | 11 +++--------
 bfd/elf32-ppc.c      |  6 +++---
 bfd/elf64-ia64-vms.c |  2 +-
 bfd/elf64-ppc.c      |  6 +++---
 bfd/elflink.c        |  8 ++++----
 5 files changed, 14 insertions(+), 19 deletions(-)

diff --git a/bfd/elf.c b/bfd/elf.c
index 346eea39b1..1b9b7fad15 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -1721,14 +1721,9 @@ _bfd_elf_print_private_bfd_data (bfd *abfd, void *farg)
       extdynsize = get_elf_backend_data (abfd)->s->sizeof_dyn;
       swap_dyn_in = get_elf_backend_data (abfd)->s->swap_dyn_in;
 
-      extdyn = dynbuf;
-      /* PR 17512: file: 6f427532.  */
-      if (s->size < extdynsize)
-	goto error_return;
-      extdynend = extdyn + s->size;
-      /* PR 17512: file: id:000006,sig:06,src:000000,op:flip4,pos:5664.
-	 Fix range check.  */
-      for (; extdyn <= (extdynend - extdynsize); extdyn += extdynsize)
+      for (extdyn = dynbuf, extdynend = dynbuf + s->size;
+	   (size_t) (extdynend - extdyn) >= extdynsize;
+	   extdyn += extdynsize)
 	{
 	  Elf_Internal_Dyn dyn;
 	  const char *name = "";
diff --git a/bfd/elf32-ppc.c b/bfd/elf32-ppc.c
index 3582711d96..1f77e18133 100644
--- a/bfd/elf32-ppc.c
+++ b/bfd/elf32-ppc.c
@@ -1852,9 +1852,9 @@ ppc_elf_get_synthetic_symtab (bfd *abfd, long symcount, asymbol **syms,
       extdynsize = get_elf_backend_data (abfd)->s->sizeof_dyn;
       swap_dyn_in = get_elf_backend_data (abfd)->s->swap_dyn_in;
 
-      extdyn = dynbuf;
-      extdynend = extdyn + dynamic->size;
-      for (; extdyn < extdynend; extdyn += extdynsize)
+      for (extdyn = dynbuf, extdynend = dynbuf + dynamic->size;
+	   (size_t) (extdynend - extdyn) >= extdynsize;
+	   extdyn += extdynsize)
 	{
 	  Elf_Internal_Dyn dyn;
 	  (*swap_dyn_in) (abfd, extdyn, &dyn);
diff --git a/bfd/elf64-ia64-vms.c b/bfd/elf64-ia64-vms.c
index 4d8f98550a..613dacd755 100644
--- a/bfd/elf64-ia64-vms.c
+++ b/bfd/elf64-ia64-vms.c
@@ -4845,7 +4845,7 @@ elf64_vms_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
 	}
 
       for (extdyn = dynbuf;
-	   extdyn < dynbuf + s->size;
+	   (size_t) (dynbuf + s->size - extdyn) >= bed->s->sizeof_dyn;
 	   extdyn += bed->s->sizeof_dyn)
 	{
 	  Elf_Internal_Dyn dyn;
diff --git a/bfd/elf64-ppc.c b/bfd/elf64-ppc.c
index cfcd263173..f1e482faed 100644
--- a/bfd/elf64-ppc.c
+++ b/bfd/elf64-ppc.c
@@ -2513,9 +2513,9 @@ ppc64_elf_get_synthetic_symtab (bfd *abfd,
 	  extdynsize = get_elf_backend_data (abfd)->s->sizeof_dyn;
 	  swap_dyn_in = get_elf_backend_data (abfd)->s->swap_dyn_in;
 
-	  extdyn = dynbuf;
-	  extdynend = extdyn + dynamic->size;
-	  for (; extdyn < extdynend; extdyn += extdynsize)
+	  for (extdyn = dynbuf, extdynend = dynbuf + dynamic->size;
+	       (size_t) (extdynend - extdyn) >= extdynsize;
+	       extdyn += extdynsize)
 	    {
 	      Elf_Internal_Dyn dyn;
 	      (*swap_dyn_in) (abfd, extdyn, &dyn);
diff --git a/bfd/elflink.c b/bfd/elflink.c
index 2b1450fa4e..89dcf26108 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -4406,7 +4406,7 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
 	  shlink = elf_elfsections (abfd)[elfsec]->sh_link;
 
 	  for (extdyn = dynbuf;
-	       extdyn <= dynbuf + s->size - bed->s->sizeof_dyn;
+	       (size_t) (dynbuf + s->size - extdyn) >= bed->s->sizeof_dyn;
 	       extdyn += bed->s->sizeof_dyn)
 	    {
 	      Elf_Internal_Dyn dyn;
@@ -8219,9 +8219,9 @@ bfd_elf_get_bfd_needed_list (bfd *abfd,
   extdynsize = get_elf_backend_data (abfd)->s->sizeof_dyn;
   swap_dyn_in = get_elf_backend_data (abfd)->s->swap_dyn_in;
 
-  extdyn = dynbuf;
-  extdynend = extdyn + s->size;
-  for (; extdyn < extdynend; extdyn += extdynsize)
+  for (extdyn = dynbuf, extdynend = dynbuf + s->size;
+       (size_t) (extdynend - extdyn) >= extdynsize;
+       extdyn += extdynsize)
     {
       Elf_Internal_Dyn dyn;
 
-- 
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