Re: PR25993, read of freed memory

[Alan Modra <amodra@gmail.com>]

On Tue, May 19, 2020 at 09:27:15AM -0400, Simon Marchi wrote:
> On 2020-05-19 12:32 a.m., Alan Modra via Gdb-patches wrote:
> > -void bfd_set_filename (bfd *abfd, char *filename);
> > +char *bfd_set_filename (bfd *abfd, const char *filename);
> 
> Should this return a `const char *`, just like bfd_get_filename?
> 
> I haven't inspected all call sites, but it sounds like the caller
> shouldn't be able to modify the filename contents.

Yes, I've updated the return type.  One minor change needed to
mach-o.c.

> Since the string gets copied by bfd_set_filename, let's use std::string
> to avoid having to free:

Done, and symfile-mem.c updated as per down-thread suggestion to make
name a const char*.

I've left the return status from bfd_set_filename in gdb unchecked,
ie. the out-of-memory NULL return, since it seems to me that not
getting the expected name change is a minor detail very likely to be
lost in some later OOM.

	PR 25993
bfd/
	* archive.c (_bfd_get_elt_at_filepos): Don't strdup filename,
	use bfd_set_filename.
	* elfcode.h (_bfd_elf_bfd_from_remote_memory): Likewise.
	* mach-o.c (bfd_mach_o_fat_member_init): Likewise.
	* opncls.c (bfd_fopen, bfd_openstreamr, bfd_openr_iovec, bfd_openw),
	(bfd_create): Likewise.
	(_bfd_delete_bfd): Don't free filename.
	(bfd_set_filename): Copy filename param to bfd_alloc'd memory,
	return pointer to the copy or NULL on alloc fail.
	* vms-lib.c (_bfd_vms_lib_get_module): Free newname and test
	result of bfd_set_filename.
	* bfd-in2.h: Regenerate.
gdb/
	* solib-darwin.c (darwin_bfd_open): Don't strdup pathname for
	bfd_set_filename.
	* solib-aix.c (solib_aix_bfd_open): Free name after calling
	bfd_set_filename.
	* symfile-mem.c (symbol_file_add_from_memory): Likewise.
ld/
	* emultempl/pe.em (gld_${EMULATION_NAME}_after_open): Don't copy
	other_bfd_filename for bfd_set_filename, and test result of
	bfd_set_filename call.  Don't create a new is->filename, simply
	copy from bfd filename.  Free new_name after bfd_set_filename.
	* emultempl/pep.em (gld_${EMULATION_NAME}_after_open): Likewise.

diff --git a/bfd/archive.c b/bfd/archive.c
index ff64727c44..1322977744 100644
--- a/bfd/archive.c
+++ b/bfd/archive.c
@@ -737,8 +737,7 @@ _bfd_get_elt_at_filepos (bfd *archive, file_ptr filepos)
   else
     {
       n_bfd->origin = n_bfd->proxy_origin;
-      n_bfd->filename = bfd_strdup (filename);
-      if (n_bfd->filename == NULL)
+      if (!bfd_set_filename (n_bfd, filename))
 	goto out;
     }
 
diff --git a/bfd/elfcode.h b/bfd/elfcode.h
index 68db3e9ee3..5e6b2a430f 100644
--- a/bfd/elfcode.h
+++ b/bfd/elfcode.h
@@ -1680,7 +1680,6 @@ NAME(_bfd_elf,bfd_from_remote_memory)
   bfd_vma high_offset;
   bfd_vma shdr_end;
   bfd_vma loadbase;  /* Bytes.  */
-  char *filename;
   size_t amt;
   unsigned int opb = bfd_octets_per_byte (templ, NULL);
 
@@ -1894,22 +1893,14 @@ NAME(_bfd_elf,bfd_from_remote_memory)
       free (contents);
       return NULL;
     }
-  filename = bfd_strdup ("<in-memory>");
-  if (filename == NULL)
-    {
-      free (bim);
-      free (contents);
-      return NULL;
-    }
   nbfd = _bfd_new_bfd ();
-  if (nbfd == NULL)
+  if (nbfd == NULL
+      || !bfd_set_filename (nbfd, "<in-memory>"))
     {
-      free (filename);
       free (bim);
       free (contents);
       return NULL;
     }
-  nbfd->filename = filename;
   nbfd->xvec = templ->xvec;
   bim->size = high_offset;
   bim->buffer = contents;
diff --git a/bfd/mach-o.c b/bfd/mach-o.c
index 33bd81e121..43fa56cb58 100644
--- a/bfd/mach-o.c
+++ b/bfd/mach-o.c
@@ -5573,26 +5573,23 @@ bfd_mach_o_fat_member_init (bfd *abfd,
   struct areltdata *areltdata;
   /* Create the member filename. Use ARCH_NAME.  */
   const bfd_arch_info_type *ap = bfd_lookup_arch (arch_type, arch_subtype);
-  char *filename;
+  const char *filename;
 
   if (ap)
     {
       /* Use the architecture name if known.  */
-      filename = bfd_strdup (ap->printable_name);
-      if (filename == NULL)
-	return FALSE;
+      filename = bfd_set_filename (abfd, ap->printable_name);
     }
   else
     {
       /* Forge a uniq id.  */
-      const size_t namelen = 2 + 8 + 1 + 2 + 8 + 1;
-      filename = bfd_malloc (namelen);
-      if (filename == NULL)
-	return FALSE;
-      snprintf (filename, namelen, "0x%lx-0x%lx",
+      char buf[2 + 8 + 1 + 2 + 8 + 1];
+      snprintf (buf, sizeof (buf), "0x%lx-0x%lx",
 		entry->cputype, entry->cpusubtype);
+      filename = bfd_set_filename (abfd, buf);
     }
-  bfd_set_filename (abfd, filename);
+  if (!filename)
+    return FALSE;
 
   areltdata = bfd_zmalloc (sizeof (struct areltdata));
   if (areltdata == NULL)
diff --git a/bfd/opncls.c b/bfd/opncls.c
index 5d3437d382..78b2ad7dd7 100644
--- a/bfd/opncls.c
+++ b/bfd/opncls.c
@@ -126,7 +126,6 @@ _bfd_delete_bfd (bfd *abfd)
       objalloc_free ((struct objalloc *) abfd->memory);
     }
 
-  free ((char *) bfd_get_filename (abfd));
   free (abfd->arelt_data);
   free (abfd);
 }
@@ -232,8 +231,7 @@ bfd_fopen (const char *filename, const char *target, const char *mode, int fd)
 
   /* PR 11983: Do not cache the original filename, but
      rather make a copy - the original might go away.  */
-  nbfd->filename = bfd_strdup (filename);
-  if (nbfd->filename == NULL)
+  if (!bfd_set_filename (nbfd, filename))
     {
       fclose (nbfd->iostream);
       _bfd_delete_bfd (nbfd);
@@ -406,8 +404,7 @@ bfd_openstreamr (const char *filename, const char *target, void *streamarg)
   nbfd->iostream = stream;
   /* PR 11983: Do not cache the original filename, but
      rather make a copy - the original might go away.  */
-  nbfd->filename = bfd_strdup (filename);
-  if (nbfd->filename == NULL)
+  if (!bfd_set_filename (nbfd, filename))
     {
       _bfd_delete_bfd (nbfd);
       return NULL;
@@ -607,8 +604,7 @@ bfd_openr_iovec (const char *filename, const char *target,
 
   /* PR 11983: Do not cache the original filename, but
      rather make a copy - the original might go away.  */
-  nbfd->filename = bfd_strdup (filename);
-  if (nbfd->filename == NULL)
+  if (!bfd_set_filename (nbfd, filename))
     {
       _bfd_delete_bfd (nbfd);
       return NULL;
@@ -679,8 +675,7 @@ bfd_openw (const char *filename, const char *target)
 
   /* PR 11983: Do not cache the original filename, but
      rather make a copy - the original might go away.  */
-  nbfd->filename = bfd_strdup (filename);
-  if (nbfd->filename == NULL)
+  if (!bfd_set_filename (nbfd, filename))
     {
       _bfd_delete_bfd (nbfd);
       return NULL;
@@ -824,8 +819,7 @@ bfd_create (const char *filename, bfd *templ)
     return NULL;
   /* PR 11983: Do not cache the original filename, but
      rather make a copy - the original might go away.  */
-  nbfd->filename = bfd_strdup (filename);
-  if (nbfd->filename == NULL)
+  if (!bfd_set_filename (nbfd, filename))
     {
       _bfd_delete_bfd (nbfd);
       return NULL;
@@ -2040,17 +2034,23 @@ FUNCTION
 	bfd_set_filename
 
 SYNOPSIS
-	void bfd_set_filename (bfd *abfd, char *filename);
+	const char *bfd_set_filename (bfd *abfd, const char *filename);
 
 DESCRIPTION
-	Set the filename of @var{abfd}.  The old filename, if any, is freed.
-	@var{filename} must be allocated using @code{xmalloc}.  After
-	this call, it is owned @var{abfd}.
+	Set the filename of @var{abfd}, copying the FILENAME parameter to
+	bfd_alloc'd memory owned by @var{abfd}.  Returns a pointer the
+	newly allocated name, or NULL if the allocation failed.
 */
 
-void
-bfd_set_filename (bfd *abfd, char *filename)
+const char *
+bfd_set_filename (bfd *abfd, const char *filename)
 {
-  free ((char *) abfd->filename);
-  abfd->filename = filename;
+  size_t len = strlen (filename) + 1;
+  char *n = bfd_alloc (abfd, len);
+  if (n)
+    {
+      memcpy (n, filename, len);
+      abfd->filename = n;
+    }
+  return n;
 }
diff --git a/bfd/vms-lib.c b/bfd/vms-lib.c
index 9504cf4976..6a8a76ecb0 100644
--- a/bfd/vms-lib.c
+++ b/bfd/vms-lib.c
@@ -1452,6 +1452,12 @@ _bfd_vms_lib_get_module (bfd *abfd, unsigned int modidx)
       break;
     }
   bfd_set_filename (res, newname);
+  free (newname);
+  if (bfd_get_filename (res) == NULL)
+    {
+      bfd_close (res);
+      return NULL;
+    }
 
   tdata->cache[modidx] = res;
 
diff --git a/gdb/solib-aix.c b/gdb/solib-aix.c
index 5da1214a25..344c1f5760 100644
--- a/gdb/solib-aix.c
+++ b/gdb/solib-aix.c
@@ -637,10 +637,10 @@ solib_aix_bfd_open (const char *pathname)
      along with appended parenthesized member name in order to allow commands
      listing all shared libraries to display.  Otherwise, we would only be
      displaying the name of the archive member object.  */
-  bfd_set_filename (object_bfd.get (),
-		    xstrprintf ("%s%s",
-				bfd_get_filename (archive_bfd.get ()),
-				sep));
+  std::string fname = string_printf ("%s%s",
+				     bfd_get_filename (archive_bfd.get ()),
+				     sep);
+  bfd_set_filename (object_bfd.get (), fname.c_str ());
 
   return object_bfd;
 }
diff --git a/gdb/solib-darwin.c b/gdb/solib-darwin.c
index e740a41fa4..ee0483d2c8 100644
--- a/gdb/solib-darwin.c
+++ b/gdb/solib-darwin.c
@@ -662,7 +662,7 @@ darwin_bfd_open (const char *pathname)
   /* The current filename for fat-binary BFDs is a name generated
      by BFD, usually a string containing the name of the architecture.
      Reset its value to the actual filename.  */
-  bfd_set_filename (res.get (), xstrdup (pathname));
+  bfd_set_filename (res.get (), pathname);
 
   return res;
 }
diff --git a/gdb/symfile-mem.c b/gdb/symfile-mem.c
index e2d2e43d7f..78096fcbae 100644
--- a/gdb/symfile-mem.c
+++ b/gdb/symfile-mem.c
@@ -78,11 +78,10 @@ target_read_memory_bfd (bfd_vma memaddr, bfd_byte *myaddr, bfd_size_type len)
    and read its in-core symbols out of inferior memory.  SIZE, if
    non-zero, is the known size of the object.  TEMPL is a bfd
    representing the target's format.  NAME is the name to use for this
-   symbol file in messages; it can be NULL or a malloc-allocated string
-   which will be attached to the BFD.  */
+   symbol file in messages; it can be NULL.  */
 static struct objfile *
 symbol_file_add_from_memory (struct bfd *templ, CORE_ADDR addr,
-			     size_t size, char *name, int from_tty)
+			     size_t size, const char *name, int from_tty)
 {
   struct objfile *objf;
   struct bfd *nbfd;
@@ -102,7 +101,7 @@ symbol_file_add_from_memory (struct bfd *templ, CORE_ADDR addr,
   gdb_bfd_ref_ptr nbfd_holder = gdb_bfd_ref_ptr::new_reference (nbfd);
 
   if (name == NULL)
-    name = xstrdup ("shared object read from target memory");
+    name = "shared object read from target memory";
   bfd_set_filename (nbfd, name);
 
   if (!bfd_check_format (nbfd, bfd_object))
@@ -183,8 +182,9 @@ add_vsyscall_page (struct target_ops *target, int from_tty)
 	  return;
 	}
 
-      char *name = xstrprintf ("system-supplied DSO at %s",
-			       paddress (target_gdbarch (), vsyscall_range.start));
+      std::string name = string_printf ("system-supplied DSO at %s",
+					paddress (target_gdbarch (),
+						  vsyscall_range.start));
       try
 	{
 	  /* Pass zero for FROM_TTY, because the action of loading the
@@ -193,7 +193,7 @@ add_vsyscall_page (struct target_ops *target, int from_tty)
 	  symbol_file_add_from_memory (bfd,
 				       vsyscall_range.start,
 				       vsyscall_range.length,
-				       name,
+				       name.c_str (),
 				       0 /* from_tty */);
 	}
       catch (const gdb_exception &ex)
diff --git a/ld/emultempl/pe.em b/ld/emultempl/pe.em
index fe65d2b266..8c5ee76233 100644
--- a/ld/emultempl/pe.em
+++ b/ld/emultempl/pe.em
@@ -1523,7 +1523,6 @@ gld_${EMULATION_NAME}_after_open (void)
 			struct bfd_symbol *s;
 			struct bfd_link_hash_entry * blhe;
 			const char *other_bfd_filename;
-			char *n;
 
 			s = (relocs[i]->sym_ptr_ptr)[0];
 
@@ -1550,9 +1549,9 @@ gld_${EMULATION_NAME}_after_open (void)
 			  continue;
 
 			/* Rename this implib to match the other one.  */
-			n = xmalloc (strlen (other_bfd_filename) + 1);
-			strcpy (n, other_bfd_filename);
-			bfd_set_filename (is->the_bfd->my_archive, n);
+			if (!bfd_set_filename (is->the_bfd->my_archive,
+					       other_bfd_filename))
+			  einfo ("%F%P: %pB: %E\n", is->the_bfd);
 		      }
 
 		    free (relocs);
@@ -1655,28 +1654,14 @@ gld_${EMULATION_NAME}_after_open (void)
 		else /* sentinel */
 		  seq = 'c';
 
-		/* PR 25993: It is possible that is->the_bfd-filename == is->filename.
-		   In which case calling bfd_set_filename on one will free the memory
-		   pointed to by the other.  */
-		if (is->filename == bfd_get_filename (is->the_bfd))
-		  {
-		    new_name = xmalloc (strlen (is->filename) + 3);
-		    sprintf (new_name, "%s.%c", is->filename, seq);
-		    bfd_set_filename (is->the_bfd, new_name);
-		    is->filename = new_name;
-		  }
-		else
-		  {
-		    new_name
-		      = xmalloc (strlen (bfd_get_filename (is->the_bfd)) + 3);
-		    sprintf (new_name, "%s.%c",
-			     bfd_get_filename (is->the_bfd), seq);
-		    bfd_set_filename (is->the_bfd, new_name);
-
-		    new_name = xmalloc (strlen (is->filename) + 3);
-		    sprintf (new_name, "%s.%c", is->filename, seq);
-		    is->filename = new_name;
-		  }
+		new_name
+		  = xmalloc (strlen (bfd_get_filename (is->the_bfd)) + 3);
+		sprintf (new_name, "%s.%c",
+			 bfd_get_filename (is->the_bfd), seq);
+		is->filename = bfd_set_filename (is->the_bfd, new_name);
+		free (new_name);
+		if (!is->filename)
+		  einfo ("%F%P: %pB: %E\n", is->the_bfd);
 	      }
 	  }
       }
diff --git a/ld/emultempl/pep.em b/ld/emultempl/pep.em
index 699b86501c..ea8e768ea9 100644
--- a/ld/emultempl/pep.em
+++ b/ld/emultempl/pep.em
@@ -1491,7 +1491,6 @@ gld_${EMULATION_NAME}_after_open (void)
 			struct bfd_symbol *s;
 			struct bfd_link_hash_entry * blhe;
 			const char *other_bfd_filename;
-			char *n;
 
 			s = (relocs[i]->sym_ptr_ptr)[0];
 
@@ -1518,9 +1517,9 @@ gld_${EMULATION_NAME}_after_open (void)
 			  continue;
 
 			/* Rename this implib to match the other one.  */
-			n = xmalloc (strlen (other_bfd_filename) + 1);
-			strcpy (n, other_bfd_filename);
-			bfd_set_filename (is->the_bfd->my_archive, n);
+			if (!bfd_set_filename (is->the_bfd->my_archive,
+					       other_bfd_filename))
+			  einfo ("%F%P: %pB: %E\n", is->the_bfd);
 		      }
 
 		    free (relocs);
@@ -1623,28 +1622,14 @@ gld_${EMULATION_NAME}_after_open (void)
 		else /* sentinel */
 		  seq = 'c';
 
-		/* PR 25993: It is possible that is->the_bfd-filename == is->filename.
-		   In which case calling bfd_set_filename on one will free the memory
-		   pointed to by the other.  */
-		if (is->filename == bfd_get_filename (is->the_bfd))
-		  {
-		    new_name = xmalloc (strlen (is->filename) + 3);
-		    sprintf (new_name, "%s.%c", is->filename, seq);
-		    bfd_set_filename (is->the_bfd, new_name);
-		    is->filename = new_name;
-		  }
-		else
-		  {
-		    new_name
-		      = xmalloc (strlen (bfd_get_filename (is->the_bfd)) + 3);
-		    sprintf (new_name, "%s.%c",
-			     bfd_get_filename (is->the_bfd), seq);
-		    bfd_set_filename (is->the_bfd, new_name);
-
-		    new_name = xmalloc (strlen (is->filename) + 3);
-		    sprintf (new_name, "%s.%c", is->filename, seq);
-		    is->filename = new_name;
-		  }
+		new_name
+		  = xmalloc (strlen (bfd_get_filename (is->the_bfd)) + 3);
+		sprintf (new_name, "%s.%c",
+			 bfd_get_filename (is->the_bfd), seq);
+		is->filename = bfd_set_filename (is->the_bfd, new_name);
+		free (new_name);
+		if (!is->filename)
+		  einfo ("%F%P: %pB: %E\n", is->the_bfd);
 	      }
 	  }
       }


-- 
Alan Modra
Australia Development Lab, IBM