[PATCH] elf: Always set l in _dl_init_paths (Bug 23462).

[Carlos O'Donell <carlos@redhat.com>]

I was doing a Fedora triage with Florian and we caught that this
issue had slipped through the cracks. Here is the patch with a
very simple test case.

8< --- 8< --- 8<
After d1d5471579eb0426671bf94f2d71e61dfb204c30 we always setup the
link map l to make the static and shared cases the same.  The bug
is that in elf/dl-load.c (_dl_init_paths) we conditionally set l
only in the #ifdef SHARED case, but unconditionally use it later.
The simple solution is to remove the #ifdef SHARED conditional,
because it's no longer needed, and unconditionally setup l for
both the static and shared cases. A regression test is added to
run a static binary with LD_LIBRARY_PATH='$ORIGIN' which crashes
before the fix and runs after the fix.

Regression tested on x86_64.
---
 ChangeLog            |  9 ++++++
 elf/Makefile         |  5 +++-
 elf/dl-load.c        | 67 +++++++++++++++++++++-----------------------
 elf/tst-dst-static.c | 30 ++++++++++++++++++++
 4 files changed, 75 insertions(+), 36 deletions(-)
 create mode 100644 elf/tst-dst-static.c

diff --git a/ChangeLog b/ChangeLog
index 2ce48223f4..cf198257ba 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2019-10-08  Carlos O'Donell  <carlos@redhat.com>
+
+	[BZ #23462]
+	* elf/Makefile (tests-static-normal): tst-dst-static.
+	(tst-dst-static-ENV): Define.
+	* elf/dl-load.c (_dl_init_paths): Remove #ifdef SHARED, and refactor
+	to always assume l is non-NULL.
+	* elf/tst-dst-static.c: New file.
+
 2019-10-07  Carlos O'Donell  <carlos@redhat.com>
 
 	* nptl/cancellation.c: Document that all functions here must be
diff --git a/elf/Makefile b/elf/Makefile
index dea51ca182..bb55baaa1f 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -148,7 +148,8 @@ endif
 tests-static-normal := tst-leaks1-static tst-array1-static tst-array5-static \
 	       tst-dl-iter-static \
 	       tst-tlsalign-static tst-tlsalign-extern-static \
-	       tst-linkall-static tst-env-setuid tst-env-setuid-tunables
+	       tst-linkall-static tst-env-setuid tst-env-setuid-tunables \
+	       tst-dst-static
 tests-static-internal := tst-tls1-static tst-tls2-static \
 	       tst-ptrguard1-static tst-stackguard1-static \
 	       tst-tls1-static-non-pie tst-libc_dlvsym-static
@@ -1557,3 +1558,5 @@ $(objpfx)tst-big-note-lib.so: $(objpfx)tst-big-note-lib.o
 $(objpfx)tst-unwind-ctor: $(objpfx)tst-unwind-ctor-lib.so
 
 CFLAGS-tst-unwind-main.c += -funwind-tables -DUSE_PTHREADS=0
+
+tst-dst-static-ENV = LD_LIBRARY_PATH='$$ORIGIN'
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 438793e53d..903f8af13a 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -748,50 +748,47 @@ _dl_init_paths (const char *llp)
   max_dirnamelen = SYSTEM_DIRS_MAX_LEN;
   *aelem = NULL;
 
-#ifdef SHARED
-  /* This points to the map of the main object.  */
+  /* This points to the map of the main object.  It is always non-NULL
+     since we have purposely made the dynamic and static cases look the
+     same.  */
   l = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
-  if (l != NULL)
+  assert (l->l_type != lt_loaded);
+
+  if (l->l_info[DT_RUNPATH])
+    {
+      /* Allocate room for the search path and fill in information
+	 from RUNPATH.  */
+      decompose_rpath (&l->l_runpath_dirs,
+		       (const void *) (D_PTR (l, l_info[DT_STRTAB])
+				       + l->l_info[DT_RUNPATH]->d_un.d_val),
+		       l, "RUNPATH");
+      /* During rtld init the memory is allocated by the stub malloc,
+	 prevent any attempt to free it by the normal malloc.  */
+      l->l_runpath_dirs.malloced = 0;
+
+      /* The RPATH is ignored.  */
+      l->l_rpath_dirs.dirs = (void *) -1;
+    }
+  else
     {
-      assert (l->l_type != lt_loaded);
+      l->l_runpath_dirs.dirs = (void *) -1;
 
-      if (l->l_info[DT_RUNPATH])
+      if (l->l_info[DT_RPATH])
 	{
 	  /* Allocate room for the search path and fill in information
-	     from RUNPATH.  */
-	  decompose_rpath (&l->l_runpath_dirs,
+	     from RPATH.  */
+	  decompose_rpath (&l->l_rpath_dirs,
 			   (const void *) (D_PTR (l, l_info[DT_STRTAB])
-					   + l->l_info[DT_RUNPATH]->d_un.d_val),
-			   l, "RUNPATH");
-	  /* During rtld init the memory is allocated by the stub malloc,
-	     prevent any attempt to free it by the normal malloc.  */
-	  l->l_runpath_dirs.malloced = 0;
-
-	  /* The RPATH is ignored.  */
-	  l->l_rpath_dirs.dirs = (void *) -1;
+					   + l->l_info[DT_RPATH]->d_un.d_val),
+			   l, "RPATH");
+	  /* During rtld init the memory is allocated by the stub
+	     malloc, prevent any attempt to free it by the normal
+	     malloc.  */
+	  l->l_rpath_dirs.malloced = 0;
 	}
       else
-	{
-	  l->l_runpath_dirs.dirs = (void *) -1;
-
-	  if (l->l_info[DT_RPATH])
-	    {
-	      /* Allocate room for the search path and fill in information
-		 from RPATH.  */
-	      decompose_rpath (&l->l_rpath_dirs,
-			       (const void *) (D_PTR (l, l_info[DT_STRTAB])
-					       + l->l_info[DT_RPATH]->d_un.d_val),
-			       l, "RPATH");
-	      /* During rtld init the memory is allocated by the stub
-		 malloc, prevent any attempt to free it by the normal
-		 malloc.  */
-	      l->l_rpath_dirs.malloced = 0;
-	    }
-	  else
-	    l->l_rpath_dirs.dirs = (void *) -1;
-	}
+	l->l_rpath_dirs.dirs = (void *) -1;
     }
-#endif	/* SHARED */
 
   if (llp != NULL && *llp != '\0')
     {
diff --git a/elf/tst-dst-static.c b/elf/tst-dst-static.c
new file mode 100644
index 0000000000..7092f24a8e
--- /dev/null
+++ b/elf/tst-dst-static.c
@@ -0,0 +1,30 @@
+/* Test DST expansion for static binaries doesn't carsh. Bug 23462.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* The purpose of this test is to exercise the code in elf/dl-loac.c
+   (_dl_init_paths) or thereabout and ensure that static binaries
+   don't crash when expanding DSTs. */
+static int
+do_test (void)
+{
+  /* If the dynamic loader code linked into the static binary cannot
+     handle expanding the DSTs e.g. null-deref on an incomplete link
+     map, then it will crash before reaching main.  */
+  return 0;
+}
+#include <support/test-driver.c>
-- 
2.21.0