commit c1cb2deeca1a85c6fc5bd41b90816d48a95bc434
Author: Florian Weimer <fweimer@redhat.com>
Date: Sun Dec 5 11:28:34 2021 +0100
elf: execve statically linked programs instead of crashing [BZ #28648]
Programs without dynamic dependencies and without a program
interpreter are now run via execve.
Previously, the dynamic linker either crashed while attempting to
read a non-existing dynamic segment (looking for DT_AUDIT/DT_DEPAUDIT
data), or the self-relocated in the static PIE executable crashed
because the outer dynamic linker had already applied RELRO protection.
<dl-execve.h> is needed because execve is not available in the
dynamic loader on Hurd.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Conflicts:
elf/Makefile
(usual test differences)
elf/rtld.c
(missing ld.so self-relocation cleanup downstream)
diff --git a/elf/Makefile b/elf/Makefile
index 118d579c42c38110..7696aa1324919a80 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -224,7 +224,8 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
tst-tls-ie tst-tls-ie-dlmopen argv0test \
tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask \
tst-tls20 tst-tls21 tst-dlmopen-dlerror tst-dlmopen-gethostbyname \
- tst-dl-is_dso tst-ro-dynamic
+ tst-dl-is_dso tst-ro-dynamic \
+ tst-rtld-run-static \
# reldep9
tests-internal += loadtest unload unload2 circleload1 \
neededtest neededtest2 neededtest3 neededtest4 \
@@ -1914,3 +1915,5 @@ $(objpfx)tst-ro-dynamic-mod.so: $(objpfx)tst-ro-dynamic-mod.os \
$(LINK.o) -nostdlib -nostartfiles -shared -o $@ \
-Wl,--script=tst-ro-dynamic-mod.map \
$(objpfx)tst-ro-dynamic-mod.os
+
+$(objpfx)tst-rtld-run-static.out: $(objpfx)/ldconfig
diff --git a/elf/rtld.c b/elf/rtld.c
index d83ac1bdc40a6081..6b0d6107801b2f44 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -50,6 +50,7 @@
#include <dl-main.h>
#include <gnu/lib-names.h>
#include <dl-tunables.h>
+#include <dl-execve.h>
#include <assert.h>
@@ -1106,6 +1107,45 @@ load_audit_modules (struct link_map *main_map, struct audit_list *audit_list)
}
}
+/* Check if the executable is not actualy dynamically linked, and
+ invoke it directly in that case. */
+static void
+rtld_chain_load (struct link_map *main_map, char *argv0)
+{
+ /* The dynamic loader run against itself. */
+ const char *rtld_soname
+ = ((const char *) D_PTR (&GL(dl_rtld_map), l_info[DT_STRTAB])
+ + GL(dl_rtld_map).l_info[DT_SONAME]->d_un.d_val);
+ if (main_map->l_info[DT_SONAME] != NULL
+ && strcmp (rtld_soname,
+ ((const char *) D_PTR (main_map, l_info[DT_STRTAB])
+ + main_map->l_info[DT_SONAME]->d_un.d_val)) == 0)
+ _dl_fatal_printf ("%s: loader cannot load itself\n", rtld_soname);
+
+ /* With DT_NEEDED dependencies, the executable is dynamically
+ linked. */
+ if (__glibc_unlikely (main_map->l_info[DT_NEEDED] != NULL))
+ return;
+
+ /* If the executable has program interpreter, it is dynamically
+ linked. */
+ for (size_t i = 0; i < main_map->l_phnum; ++i)
+ if (main_map->l_phdr[i].p_type == PT_INTERP)
+ return;
+
+ const char *pathname = _dl_argv[0];
+ if (argv0 != NULL)
+ _dl_argv[0] = argv0;
+ int errcode = __rtld_execve (pathname, _dl_argv, _environ);
+ const char *errname = strerrorname_np (errcode);
+ if (errname != NULL)
+ _dl_fatal_printf("%s: cannot execute %s: %s\n",
+ rtld_soname, pathname, errname);
+ else
+ _dl_fatal_printf("%s: cannot execute %s: %d\n",
+ rtld_soname, pathname, errno);
+}
+
static void
dl_main (const ElfW(Phdr) *phdr,
ElfW(Word) phnum,
@@ -1374,14 +1414,8 @@ dl_main (const ElfW(Phdr) *phdr,
/* Now the map for the main executable is available. */
main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
- if (__glibc_likely (state.mode == rtld_mode_normal)
- && GL(dl_rtld_map).l_info[DT_SONAME] != NULL
- && main_map->l_info[DT_SONAME] != NULL
- && strcmp ((const char *) D_PTR (&GL(dl_rtld_map), l_info[DT_STRTAB])
- + GL(dl_rtld_map).l_info[DT_SONAME]->d_un.d_val,
- (const char *) D_PTR (main_map, l_info[DT_STRTAB])
- + main_map->l_info[DT_SONAME]->d_un.d_val) == 0)
- _dl_fatal_printf ("loader cannot load itself\n");
+ if (__glibc_likely (state.mode == rtld_mode_normal))
+ rtld_chain_load (main_map, argv0);
phdr = main_map->l_phdr;
phnum = main_map->l_phnum;
diff --git a/elf/tst-rtld-run-static.c b/elf/tst-rtld-run-static.c
new file mode 100644
index 0000000000000000..7281093504b675c4
--- /dev/null
+++ b/elf/tst-rtld-run-static.c
@@ -0,0 +1,62 @@
+/* Test running statically linked programs using ld.so.
+ Copyright (C) 2021 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/check.h>
+#include <support/support.h>
+#include <support/capture_subprocess.h>
+#include <string.h>
+#include <stdlib.h>
+
+static int
+do_test (void)
+{
+ char *ldconfig_path = xasprintf ("%s/elf/ldconfig", support_objdir_root);
+
+ {
+ char *argv[] = { (char *) "ld.so", ldconfig_path, (char *) "--help", NULL };
+ struct support_capture_subprocess cap
+ = support_capture_subprogram (support_objdir_elf_ldso, argv);
+ support_capture_subprocess_check (&cap, "no --argv0", 0, sc_allow_stdout);
+ puts ("info: output without --argv0:");
+ puts (cap.out.buffer);
+ TEST_VERIFY (strstr (cap.out.buffer, "Usage: ldconfig [OPTION...]\n")
+ == cap.out.buffer);
+ support_capture_subprocess_free (&cap);
+ }
+
+ {
+ char *argv[] =
+ {
+ (char *) "ld.so", (char *) "--argv0", (char *) "ldconfig-argv0",
+ ldconfig_path, (char *) "--help", NULL
+ };
+ struct support_capture_subprocess cap
+ = support_capture_subprogram (support_objdir_elf_ldso, argv);
+ support_capture_subprocess_check (&cap, "with --argv0", 0, sc_allow_stdout);
+ puts ("info: output with --argv0:");
+ puts (cap.out.buffer);
+ TEST_VERIFY (strstr (cap.out.buffer, "Usage: ldconfig-argv0 [OPTION...]\n")
+ == cap.out.buffer);
+ support_capture_subprocess_free (&cap);
+ }
+
+ free (ldconfig_path);
+ return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/generic/dl-execve.h b/sysdeps/generic/dl-execve.h
new file mode 100644
index 0000000000000000..5fd097df69e1770c
--- /dev/null
+++ b/sysdeps/generic/dl-execve.h
@@ -0,0 +1,25 @@
+/* execve for the dynamic linker. Generic stub version.
+ Copyright (C) 2021 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 <errno.h>
+
+static int
+__rtld_execve (const char *path, char *const *argv, char *const *envp)
+{
+ return ENOSYS;
+}
diff --git a/sysdeps/unix/sysv/linux/dl-execve.h b/sysdeps/unix/sysv/linux/dl-execve.h
new file mode 100644
index 0000000000000000..ead3e1c28da34363
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/dl-execve.h
@@ -0,0 +1,25 @@
+/* execve for the dynamic linker. Linux version.
+ Copyright (C) 2021 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 <errno.h>
+
+static inline int
+__rtld_execve (const char *path, char *const *argv, char *const *envp)
+{
+ return -INTERNAL_SYSCALL_CALL (execve, path, argv, envp);
+}