From aa3d7bd5299b33bffc118aa618b59bfa66059bcb Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Thu, 13 Feb 2025 21:56:52 +0100
Subject: [PATCH] elf: Keep using minimal malloc after early DTV resize (bug
 32412)

If an auditor loads many TLS-using modules during startup, it is
possible to trigger DTV resizing.  Previously, the DTV was marked
as allocated by the main malloc afterwards, even if the minimal
malloc was still in use.  With this change, _dl_resize_dtv marks
the resized DTV as allocated with the minimal malloc.

The new test reuses TLS-using modules from other auditing tests.

Reviewed-by: DJ Delorie <dj@redhat.com>
---
 elf/Makefile                    |  5 +++
 elf/dl-tls.c                    |  7 ++++
 elf/tst-audit-tlsdesc-dlopen2.c | 46 +++++++++++++++++++++++++
 elf/tst-auditmod-tlsdesc2.c     | 59 +++++++++++++++++++++++++++++++++
 4 files changed, 117 insertions(+)
 create mode 100644 elf/tst-audit-tlsdesc-dlopen2.c
 create mode 100644 elf/tst-auditmod-tlsdesc2.c

diff --git a/elf/Makefile b/elf/Makefile
index 5c833871d0..1ea0e7037e 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -379,6 +379,7 @@ tests += \
   tst-align3 \
   tst-audit-tlsdesc \
   tst-audit-tlsdesc-dlopen \
+  tst-audit-tlsdesc-dlopen2 \
   tst-audit1 \
   tst-audit2 \
   tst-audit8 \
@@ -863,6 +864,7 @@ modules-names += \
   tst-auditmanymod8 \
   tst-auditmanymod9 \
   tst-auditmod-tlsdesc  \
+  tst-auditmod-tlsdesc2 \
   tst-auditmod1 \
   tst-auditmod11 \
   tst-auditmod12 \
@@ -3189,6 +3191,9 @@ $(objpfx)tst-audit-tlsdesc.out: $(objpfx)tst-auditmod-tlsdesc.so
 tst-audit-tlsdesc-ENV = LD_AUDIT=$(objpfx)tst-auditmod-tlsdesc.so
 $(objpfx)tst-audit-tlsdesc-dlopen.out: $(objpfx)tst-auditmod-tlsdesc.so
 tst-audit-tlsdesc-dlopen-ENV = LD_AUDIT=$(objpfx)tst-auditmod-tlsdesc.so
+$(objpfx)tst-audit-tlsdesc-dlopen2.out: $(objpfx)tst-auditmod-tlsdesc2.so \
+  $(patsubst %, $(objpfx)%.so, $(tlsmod17a-modules))
+tst-audit-tlsdesc-dlopen2-ENV = LD_AUDIT=$(objpfx)tst-auditmod-tlsdesc2.so
 
 $(objpfx)tst-dlmopen-twice.out: \
   $(objpfx)tst-dlmopen-twice-mod1.so \
diff --git a/elf/dl-tls.c b/elf/dl-tls.c
index 5178d9b66a..a083a82933 100644
--- a/elf/dl-tls.c
+++ b/elf/dl-tls.c
@@ -566,6 +566,13 @@ _dl_resize_dtv (dtv_t *dtv, size_t max_modid)
       if (newp == NULL)
 	oom ();
       memcpy (newp, &dtv[-1], (2 + oldsize) * sizeof (dtv_t));
+#ifdef SHARED
+      /* Auditors can trigger a DTV resize event while the full malloc
+	 is not yet in use.  Mark the new DTV allocation as the
+	 initial allocation.  */
+      if (!__rtld_malloc_is_complete ())
+	GL(dl_initial_dtv) = &newp[1];
+#endif
     }
   else
     {
diff --git a/elf/tst-audit-tlsdesc-dlopen2.c b/elf/tst-audit-tlsdesc-dlopen2.c
new file mode 100644
index 0000000000..7ba2c4129a
--- /dev/null
+++ b/elf/tst-audit-tlsdesc-dlopen2.c
@@ -0,0 +1,46 @@
+/* Loading TLS-using modules from auditors (bug 32412).  Main program.
+   Copyright (C) 2021-2025 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/>.  */
+
+#include <support/xdlfcn.h>
+#include <stdio.h>
+
+static int
+do_test (void)
+{
+  puts ("info: start of main program");
+
+  /* Load TLS-using modules, to trigger DTV resizing.  The dynamic
+     linker will load them again (requiring their own TLS) because the
+     dlopen calls from the auditor were in the auditing namespace.  */
+  for (int i = 1; i <= 19; ++i)
+    {
+      char dso[30];
+      snprintf (dso, sizeof (dso), "tst-tlsmod17a%d.so", i);
+      char sym[30];
+      snprintf (sym, sizeof(sym), "tlsmod17a%d", i);
+
+      void *handle = xdlopen (dso, RTLD_LAZY);
+      int (*func) (void) = xdlsym (handle, sym);
+      /* Trigger TLS allocation.  */
+      func ();
+    }
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/elf/tst-auditmod-tlsdesc2.c b/elf/tst-auditmod-tlsdesc2.c
new file mode 100644
index 0000000000..50275cd34d
--- /dev/null
+++ b/elf/tst-auditmod-tlsdesc2.c
@@ -0,0 +1,59 @@
+/* Loading TLS-using modules from auditors (bug 32412).  Audit module.
+   Copyright (C) 2021-2025 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/>.  */
+
+#include <dlfcn.h>
+#include <link.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <unistd.h>
+
+unsigned int
+la_version (unsigned int version)
+{
+  /* Open some modules, to trigger DTV resizing before the switch to
+     the main malloc.  */
+  for (int i = 1; i <= 19; ++i)
+    {
+      char dso[30];
+      snprintf (dso, sizeof (dso), "tst-tlsmod17a%d.so", i);
+      char sym[30];
+      snprintf (sym, sizeof(sym), "tlsmod17a%d", i);
+
+      void *handle = dlopen (dso, RTLD_LAZY);
+      if (handle == NULL)
+        {
+          printf ("error: dlmopen from auditor: %s\n", dlerror  ());
+          fflush (stdout);
+          _exit (1);
+        }
+      int (*func) (void) = dlsym (handle, sym);
+      if (func == NULL)
+        {
+          printf ("error: dlsym from auditor: %s\n", dlerror  ());
+          fflush (stdout);
+          _exit (1);
+        }
+      /* Trigger TLS allocation.  */
+      func ();
+    }
+
+  puts ("info: TLS-using modules loaded from auditor");
+  fflush (stdout);
+
+  return LAV_CURRENT;
+}
-- 
2.27.0

