Bug 23686, two segment faults in nm

[Alan Modra <amodra@gmail.com>]

Fixes the bugs exposed by the testcases in the PR, plus two more bugs
I noticed when looking at _bfd_stab_section_find_nearest_line.

	PR 23686
	* dwarf2.c (read_section): Error when attempting to malloc
	"(bfd_size_type) -1".
	* syms.c (_bfd_stab_section_find_nearest_line): Bounds check
	function_name.  Bounds check reloc address.  Formatting.  Ensure
	.stabstr zero terminated.

diff --git a/bfd/dwarf2.c b/bfd/dwarf2.c
index 3b2885599e..77a7368dc0 100644
--- a/bfd/dwarf2.c
+++ b/bfd/dwarf2.c
@@ -527,6 +527,7 @@ read_section (bfd *	      abfd,
   asection *msec;
   const char *section_name = sec->uncompressed_name;
   bfd_byte *contents = *section_buffer;
+  bfd_size_type amt;
 
   /* The section may have already been read.  */
   if (contents == NULL)
@@ -549,7 +550,13 @@ read_section (bfd *	      abfd,
       *section_size = msec->rawsize ? msec->rawsize : msec->size;
       /* Paranoia - alloc one extra so that we can make sure a string
 	 section is NUL terminated.  */
-      contents = (bfd_byte *) bfd_malloc (*section_size + 1);
+      amt = *section_size + 1;
+      if (amt == 0)
+	{
+	  bfd_set_error (bfd_error_no_memory);
+	  return FALSE;
+	}
+      contents = (bfd_byte *) bfd_malloc (amt);
       if (contents == NULL)
 	return FALSE;
       if (syms
diff --git a/bfd/syms.c b/bfd/syms.c
index 187071fada..e09640ab74 100644
--- a/bfd/syms.c
+++ b/bfd/syms.c
@@ -1035,6 +1035,10 @@ _bfd_stab_section_find_nearest_line (bfd *abfd,
 					 0, strsize))
 	return FALSE;
 
+      /* Stab strings ought to be nul terminated.  Ensure the last one
+	 is, to prevent running off the end of the buffer.  */
+      info->strs[strsize - 1] = 0;
+
       /* If this is a relocatable object file, we have to relocate
 	 the entries in .stab.  This should always be simple 32 bit
 	 relocations against symbols defined in this object file, so
@@ -1073,7 +1077,8 @@ _bfd_stab_section_find_nearest_line (bfd *abfd,
 		  || r->howto->bitsize != 32
 		  || r->howto->pc_relative
 		  || r->howto->bitpos != 0
-		  || r->howto->dst_mask != 0xffffffff)
+		  || r->howto->dst_mask != 0xffffffff
+		  || r->address * bfd_octets_per_byte (abfd) + 4 > stabsize)
 		{
 		  _bfd_error_handler
 		    (_("unsupported .stab relocation"));
@@ -1195,7 +1200,8 @@ _bfd_stab_section_find_nearest_line (bfd *abfd,
 		{
 		  nul_fun = stab;
 		  nul_str = str;
-		  if (file_name >= (char *) info->strs + strsize || file_name < (char *) str)
+		  if (file_name >= (char *) info->strs + strsize
+		      || file_name < (char *) str)
 		    file_name = NULL;
 		  if (stab + STABSIZE + TYPEOFF < info->stabs + stabsize
 		      && *(stab + STABSIZE + TYPEOFF) == (bfd_byte) N_SO)
@@ -1206,7 +1212,8 @@ _bfd_stab_section_find_nearest_line (bfd *abfd,
 		      directory_name = file_name;
 		      file_name = ((char *) str
 				   + bfd_get_32 (abfd, stab + STRDXOFF));
-		      if (file_name >= (char *) info->strs + strsize || file_name < (char *) str)
+		      if (file_name >= (char *) info->strs + strsize
+			  || file_name < (char *) str)
 			file_name = NULL;
 		    }
 		}
@@ -1217,7 +1224,8 @@ _bfd_stab_section_find_nearest_line (bfd *abfd,
 	      file_name = (char *) str + bfd_get_32 (abfd, stab + STRDXOFF);
 	      /* PR 17512: file: 0c680a1f.  */
 	      /* PR 17512: file: 5da8aec4.  */
-	      if (file_name >= (char *) info->strs + strsize || file_name < (char *) str)
+	      if (file_name >= (char *) info->strs + strsize
+		  || file_name < (char *) str)
 		file_name = NULL;
 	      break;
 
@@ -1226,7 +1234,8 @@ _bfd_stab_section_find_nearest_line (bfd *abfd,
 	      function_name = (char *) str + bfd_get_32 (abfd, stab + STRDXOFF);
 	      if (function_name == (char *) str)
 		continue;
-	      if (function_name >= (char *) info->strs + strsize)
+	      if (function_name >= (char *) info->strs + strsize
+		  || function_name < (char *) str)
 		function_name = NULL;
 
 	      nul_fun = NULL;
@@ -1335,7 +1344,8 @@ _bfd_stab_section_find_nearest_line (bfd *abfd,
 	  if (val <= offset)
 	    {
 	      file_name = (char *) str + bfd_get_32 (abfd, stab + STRDXOFF);
-	      if (file_name >= (char *) info->strs + strsize || file_name < (char *) str)
+	      if (file_name >= (char *) info->strs + strsize
+		  || file_name < (char *) str)
 		file_name = NULL;
 	      *pline = 0;
 	    }

-- 
Alan Modra
Australia Development Lab, IBM