* [PATCH v3 1/4] elf: Consolidate stackinfo.h
2024-06-18 19:40 [PATCH v3 0/4] Improve executable stack handling Adhemerval Zanella
@ 2024-06-18 19:40 ` Adhemerval Zanella
2024-06-18 19:40 ` [PATCH v3 2/4] elf: Do not change stack permission on dlopen/dlmopen Adhemerval Zanella
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Adhemerval Zanella @ 2024-06-18 19:40 UTC (permalink / raw)
To: libc-alpha; +Cc: H . J . Lu, Florian Weimer, Zack Weinberg
And use sane default the generic implementation.
---
sysdeps/aarch64/stackinfo.h | 33 ---------------------
sysdeps/arc/stackinfo.h | 33 ---------------------
sysdeps/csky/stackinfo.h | 29 ------------------
sysdeps/generic/stackinfo.h | 15 ++++++++--
sysdeps/loongarch/stackinfo.h | 33 ---------------------
sysdeps/nios2/stackinfo.h | 33 ---------------------
sysdeps/powerpc/{ => powerpc32}/stackinfo.h | 8 +----
sysdeps/riscv/stackinfo.h | 33 ---------------------
8 files changed, 13 insertions(+), 204 deletions(-)
delete mode 100644 sysdeps/aarch64/stackinfo.h
delete mode 100644 sysdeps/arc/stackinfo.h
delete mode 100644 sysdeps/csky/stackinfo.h
delete mode 100644 sysdeps/loongarch/stackinfo.h
delete mode 100644 sysdeps/nios2/stackinfo.h
rename sysdeps/powerpc/{ => powerpc32}/stackinfo.h (82%)
delete mode 100644 sysdeps/riscv/stackinfo.h
diff --git a/sysdeps/aarch64/stackinfo.h b/sysdeps/aarch64/stackinfo.h
deleted file mode 100644
index 5a4dce7309..0000000000
--- a/sysdeps/aarch64/stackinfo.h
+++ /dev/null
@@ -1,33 +0,0 @@
-/* Copyright (C) 2001-2024 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/>. */
-
-/* This file contains a bit of information about the stack allocation
- of the processor. */
-
-#ifndef _STACKINFO_H
-#define _STACKINFO_H 1
-
-#include <elf.h>
-
-/* On AArch64 the stack grows down. */
-#define _STACK_GROWS_DOWN 1
-
-/* Default to a non-executable stack. */
-#define DEFAULT_STACK_PERMS (PF_R|PF_W)
-
-#endif /* stackinfo.h */
diff --git a/sysdeps/arc/stackinfo.h b/sysdeps/arc/stackinfo.h
deleted file mode 100644
index 99a7f56ea0..0000000000
--- a/sysdeps/arc/stackinfo.h
+++ /dev/null
@@ -1,33 +0,0 @@
-/* Stack environment definitions for ARC.
- Copyright (C) 2020-2024 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/>. */
-
-/* This file contains a bit of information about the stack allocation
- of the processor. */
-
-#ifndef _STACKINFO_H
-#define _STACKINFO_H 1
-
-#include <elf.h>
-
-/* On ARC the stack grows down. */
-#define _STACK_GROWS_DOWN 1
-
-/* Default to a non-executable stack. */
-#define DEFAULT_STACK_PERMS (PF_R|PF_W)
-
-#endif /* stackinfo.h */
diff --git a/sysdeps/csky/stackinfo.h b/sysdeps/csky/stackinfo.h
deleted file mode 100644
index ef22fa3249..0000000000
--- a/sysdeps/csky/stackinfo.h
+++ /dev/null
@@ -1,29 +0,0 @@
-/* Stack environment definitions. C-SKY version.
- Copyright (C) 2018-2024 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/>. */
-
-#ifndef _STACKINFO_H
-#define _STACKINFO_H 1
-
-#include <elf.h>
-
-/* On C-SKY the stack grows down. */
-#define _STACK_GROWS_DOWN 1
-
-#define DEFAULT_STACK_PERMS (PF_R|PF_W)
-
-#endif /* stackinfo.h */
diff --git a/sysdeps/generic/stackinfo.h b/sysdeps/generic/stackinfo.h
index bf752ce94d..51e5f92055 100644
--- a/sysdeps/generic/stackinfo.h
+++ b/sysdeps/generic/stackinfo.h
@@ -15,6 +15,15 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
-/* This file contains a bit of information about the stack allocation
- of the processor. Since there is no general truth we can't say
- anything here. */
+/* This file contains a bit of information about the stack allocation of the
+ processor. Default to a non executable stack that grows downwards. */
+
+#ifndef _STACKINFO_H
+#define _STACKINFO_H 1
+
+#include <elf.h>
+
+#define _STACK_GROWS_DOWN 1
+#define DEFAULT_STACK_PERMS (PF_R|PF_W)
+
+#endif
diff --git a/sysdeps/loongarch/stackinfo.h b/sysdeps/loongarch/stackinfo.h
deleted file mode 100644
index 6ee50552b7..0000000000
--- a/sysdeps/loongarch/stackinfo.h
+++ /dev/null
@@ -1,33 +0,0 @@
-/* Stack environment definitions for LoongArch.
- Copyright (C) 2022-2024 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/>. */
-
-/* This file contains a bit of information about the stack allocation
- of the processor. */
-
-#ifndef _STACKINFO_H
-#define _STACKINFO_H 1
-
-#include <elf.h>
-
-/* On LoongArch the stack grows down. */
-#define _STACK_GROWS_DOWN 1
-
-/* Default to a non-executable stack. */
-#define DEFAULT_STACK_PERMS (PF_R | PF_W)
-
-#endif /* stackinfo.h */
diff --git a/sysdeps/nios2/stackinfo.h b/sysdeps/nios2/stackinfo.h
deleted file mode 100644
index e67d53ee87..0000000000
--- a/sysdeps/nios2/stackinfo.h
+++ /dev/null
@@ -1,33 +0,0 @@
-/* Stack environment definitions for Nios II.
- Copyright (C) 2012-2024 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/>. */
-
-/* This file contains a bit of information about the stack allocation
- of the processor. */
-
-#ifndef _STACKINFO_H
-#define _STACKINFO_H 1
-
-#include <elf.h>
-
-/* On Nios II the stack grows down. */
-#define _STACK_GROWS_DOWN 1
-
-/* Default to a non-executable stack. */
-#define DEFAULT_STACK_PERMS (PF_R|PF_W)
-
-#endif /* stackinfo.h */
diff --git a/sysdeps/powerpc/stackinfo.h b/sysdeps/powerpc/powerpc32/stackinfo.h
similarity index 82%
rename from sysdeps/powerpc/stackinfo.h
rename to sysdeps/powerpc/powerpc32/stackinfo.h
index 410689bc27..2ca360068a 100644
--- a/sysdeps/powerpc/stackinfo.h
+++ b/sysdeps/powerpc/powerpc32/stackinfo.h
@@ -26,13 +26,7 @@
/* On PPC the stack grows down. */
#define _STACK_GROWS_DOWN 1
-#if __WORDSIZE == 64
-/* PPC64 doesn't need an executable stack and doesn't need PT_GNU_STACK
- * to make the stack nonexecutable. */
-# define DEFAULT_STACK_PERMS (PF_R|PF_W)
-#else
/* PF_X can be overridden if PT_GNU_STACK is present but is presumed absent. */
-# define DEFAULT_STACK_PERMS (PF_R|PF_W|PF_X)
-#endif
+#define DEFAULT_STACK_PERMS (PF_R|PF_W|PF_X)
#endif /* stackinfo.h */
diff --git a/sysdeps/riscv/stackinfo.h b/sysdeps/riscv/stackinfo.h
deleted file mode 100644
index a786d4f9b0..0000000000
--- a/sysdeps/riscv/stackinfo.h
+++ /dev/null
@@ -1,33 +0,0 @@
-/* Stack environment definitions for RISC-V.
- Copyright (C) 2011-2024 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/>. */
-
-/* This file contains a bit of information about the stack allocation
- of the processor. */
-
-#ifndef _STACKINFO_H
-#define _STACKINFO_H 1
-
-#include <elf.h>
-
-/* On RISC-V the stack grows down. */
-#define _STACK_GROWS_DOWN 1
-
-/* Default to a non-executable stack. */
-#define DEFAULT_STACK_PERMS (PF_R | PF_W)
-
-#endif /* stackinfo.h */
--
2.43.0
^ permalink raw reply [flat|nested] 5+ messages in thread* [PATCH v3 2/4] elf: Do not change stack permission on dlopen/dlmopen
2024-06-18 19:40 [PATCH v3 0/4] Improve executable stack handling Adhemerval Zanella
2024-06-18 19:40 ` [PATCH v3 1/4] elf: Consolidate stackinfo.h Adhemerval Zanella
@ 2024-06-18 19:40 ` Adhemerval Zanella
2024-06-18 19:40 ` [PATCH v3 3/4] elf: Add tst-execstack-prog-static Adhemerval Zanella
2024-06-18 19:40 ` [PATCH v3 4/4] elf: Add glibc.rtld.execstack Adhemerval Zanella
3 siblings, 0 replies; 5+ messages in thread
From: Adhemerval Zanella @ 2024-06-18 19:40 UTC (permalink / raw)
To: libc-alpha; +Cc: H . J . Lu, Florian Weimer, Zack Weinberg
If some shared library loaded with dlopen/dlmopen requires an executable
stack, either implicitly because of a missing GNU_STACK ELF header
(where the ABI default flags implies in the executable bit) or explicitly
because of the executable bit from GNU_STACK; the loader will try to set
the both the main thread and all thread stacks (from the pthread cache)
as executable.
Besides the issue where any __nptl_change_stack_perm failure does not
undo the previous executable transition (meaning that if the library
fails to load, there can be thread stacks with executable stacks), this
behavior was used on recent CVE [1] as a vector for RCE.
This patch changes that if a shared library requires an executable
stack, and the current stack is not executable, dlopen fails. The
change is done only for dynamically loaded modules, if the program
or any dependency requires an executable stack, the loader will still
change the main thread before program execution and any thread created
with default stack configuration.
[1] https://www.qualys.com/2023/07/19/cve-2023-38408/rce-openssh-forwarded-ssh-agent.txt
Checked on x86_64-linux-gnu and i686-linux-gnu.
---
NEWS | 8 ++
elf/dl-load.c | 11 +-
elf/tst-execstack.c | 142 ++++++++++---------------
nptl/allocatestack.c | 19 ----
sysdeps/nptl/pthreadP.h | 6 --
sysdeps/unix/sysv/linux/Versions | 3 -
sysdeps/unix/sysv/linux/dl-execstack.c | 67 +-----------
sysdeps/unix/sysv/linux/mips/Makefile | 7 ++
8 files changed, 79 insertions(+), 184 deletions(-)
diff --git a/NEWS b/NEWS
index 20e263f581..43ff2ee23b 100644
--- a/NEWS
+++ b/NEWS
@@ -47,6 +47,14 @@ Deprecated and removed features, and other changes affecting compatibility:
<utmpx.h> (except for login_tty) due to locking and session management
problems.
+* dlopen and dlmopen do not make the stack executable if the shared
+ library requires it and the stack is not already executable. If the
+ program requires an executable stack, either implicitly because of
+ a missing GNU_STACK ELF header (and default ABI permission having the
+ executable bit set) or explicitly because of the executable bit in
+ GNU_STACK, glibc will change the main thread, and any created thread
+ stack executable.
+
Changes to build and runtime requirements:
[Add changes to build and runtime requirements here]
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 8a89b71016..015595aac4 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1298,12 +1298,17 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
if (__glibc_unlikely ((stack_flags &~ GL(dl_stack_flags)) & PF_X))
{
/* The stack is presently not executable, but this module
- requires that it be executable. */
+ requires that it be executable. Only tries to change the
+ stack protection during process startup. */
+ if ((mode & __RTLD_DLOPEN) == 0)
#if PTHREAD_IN_LIBC
- errval = _dl_make_stacks_executable (stack_endp);
+ errval = _dl_make_stacks_executable (stack_endp);
#else
- errval = (*GL(dl_make_stack_executable_hook)) (stack_endp);
+ errval = (*GL(dl_make_stack_executable_hook)) (stack_endp);
#endif
+ else
+ errval = EINVAL;
+
if (errval)
{
errstring = N_("\
diff --git a/elf/tst-execstack.c b/elf/tst-execstack.c
index 560b353918..cd758c089e 100644
--- a/elf/tst-execstack.c
+++ b/elf/tst-execstack.c
@@ -9,6 +9,11 @@
#include <error.h>
#include <stackinfo.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/xthread.h>
+#include <support/xdlfcn.h>
+
static void
print_maps (void)
{
@@ -20,11 +25,21 @@ print_maps (void)
#endif
}
-static void deeper (void (*f) (void));
+#ifndef DEFAULT_RWX_STACK
+# define DEFAULT_RWX_STACK 0
+#else
+static void
+deeper (void (*f) (void))
+{
+ char stack[1100 * 1024];
+ explicit_bzero (stack, sizeof stack);
+ (*f) ();
+ memfrob (stack, sizeof stack);
+}
+#endif
#if USE_PTHREADS
-# include <pthread.h>
-
+# if DEFAULT_RWX_STACK
static void *
tryme_thread (void *f)
{
@@ -32,16 +47,21 @@ tryme_thread (void *f)
return 0;
}
+# endif
static pthread_barrier_t startup_barrier, go_barrier;
static void *
waiter_thread (void *arg)
{
- void **f = arg;
- pthread_barrier_wait (&startup_barrier);
- pthread_barrier_wait (&go_barrier);
+ xpthread_barrier_wait (&startup_barrier);
+ xpthread_barrier_wait (&go_barrier);
+# if DEFAULT_RWX_STACK
+ void **f = arg;
(*((void (*) (void)) *f)) ();
+# else
+ abort ();
+# endif
return 0;
}
@@ -83,52 +103,36 @@ do_test (void)
printf ("executable stacks %sallowed\n", allow_execstack ? "" : "not ");
+#if USE_PTHREADS || DEFAULT_RWX_STACK
static void *f; /* Address of this is used in other threads. */
+#endif
#if USE_PTHREADS
/* Create some threads while stacks are nonexecutable. */
#define N 5
- pthread_t thr[N];
- pthread_barrier_init (&startup_barrier, NULL, N + 1);
- pthread_barrier_init (&go_barrier, NULL, N + 1);
+ xpthread_barrier_init (&startup_barrier, NULL, N + 1);
+ xpthread_barrier_init (&go_barrier, NULL, N + 1);
for (int i = 0; i < N; ++i)
- {
- int rc = pthread_create (&thr[i], NULL, &waiter_thread, &f);
- if (rc)
- error (1, rc, "pthread_create");
- }
+ xpthread_create (NULL, &waiter_thread, &f);
/* Make sure they are all there using their stacks. */
- pthread_barrier_wait (&startup_barrier);
+ xpthread_barrier_wait (&startup_barrier);
puts ("threads waiting");
#endif
print_maps ();
-#if USE_PTHREADS
+#if USE_PTHREADS && DEFAULT_RWX_STACK
void *old_stack_addr, *new_stack_addr;
size_t stack_size;
pthread_t me = pthread_self ();
pthread_attr_t attr;
- int ret = 0;
-
- ret = pthread_getattr_np (me, &attr);
- if (ret)
- {
- printf ("before execstack: pthread_getattr_np returned error: %s\n",
- strerror (ret));
- return 1;
- }
- ret = pthread_attr_getstack (&attr, &old_stack_addr, &stack_size);
- if (ret)
- {
- printf ("before execstack: pthread_attr_getstack returned error: %s\n",
- strerror (ret));
- return 1;
- }
+ TEST_VERIFY_EXIT (pthread_getattr_np (me, &attr) == 0);
+ TEST_VERIFY_EXIT (pthread_attr_getstack (&attr, &old_stack_addr,
+ &stack_size) == 0);
# if _STACK_GROWS_DOWN
old_stack_addr += stack_size;
# else
@@ -143,18 +147,12 @@ do_test (void)
const char *soname = "tst-execstack-mod.so";
#endif
void *h = dlopen (soname, RTLD_LAZY);
- if (h == NULL)
- {
- printf ("cannot load: %s\n", dlerror ());
- return allow_execstack;
- }
+#if !DEFAULT_RWX_STACK
+ TEST_VERIFY_EXIT (h == NULL);
+#else
+ TEST_VERIFY_EXIT (h != NULL);
- f = dlsym (h, "tryme");
- if (f == NULL)
- {
- printf ("symbol not found: %s\n", dlerror ());
- return 1;
- }
+ f = xdlsym (h, "tryme");
/* Test if that really made our stack executable.
The `tryme' function should crash if not. */
@@ -163,28 +161,15 @@ do_test (void)
print_maps ();
-#if USE_PTHREADS
- ret = pthread_getattr_np (me, &attr);
- if (ret)
- {
- printf ("after execstack: pthread_getattr_np returned error: %s\n",
- strerror (ret));
- return 1;
- }
-
- ret = pthread_attr_getstack (&attr, &new_stack_addr, &stack_size);
- if (ret)
- {
- printf ("after execstack: pthread_attr_getstack returned error: %s\n",
- strerror (ret));
- return 1;
- }
-
-# if _STACK_GROWS_DOWN
+# if USE_PTHREADS
+ TEST_VERIFY_EXIT (pthread_getattr_np (me, &attr) == 0);
+ TEST_VERIFY_EXIT (pthread_attr_getstack (&attr, &new_stack_addr,
+ &stack_size) == 0);
+# if _STACK_GROWS_DOWN
new_stack_addr += stack_size;
-# else
+# else
new_stack_addr -= stack_size;
-# endif
+# endif
/* It is possible that the dlopen'd module may have been mmapped just below
the stack. The stack size is taken as MIN(stack rlimit size, end of last
@@ -194,48 +179,29 @@ do_test (void)
stacksize and stackaddr respectively. If the size changes due to the
above, then both stacksize and stackaddr can change, but the stack bottom
should remain the same, which is computed as stackaddr + stacksize. */
- if (old_stack_addr != new_stack_addr)
- {
- printf ("Stack end changed, old: %p, new: %p\n",
- old_stack_addr, new_stack_addr);
- return 1;
- }
+ TEST_VERIFY_EXIT (old_stack_addr == new_stack_addr);
printf ("Stack address remains the same: %p\n", old_stack_addr);
-#endif
+# endif
/* Test that growing the stack region gets new executable pages too. */
deeper ((void (*) (void)) f);
print_maps ();
-#if USE_PTHREADS
+# if USE_PTHREADS
/* Test that a fresh thread now gets an executable stack. */
- {
- pthread_t th;
- int rc = pthread_create (&th, NULL, &tryme_thread, f);
- if (rc)
- error (1, rc, "pthread_create");
- }
+ xpthread_create (NULL, &tryme_thread, f);
puts ("threads go");
/* The existing threads' stacks should have been changed.
Let them run to test it. */
- pthread_barrier_wait (&go_barrier);
+ xpthread_barrier_wait (&go_barrier);
pthread_exit ((void *) (long int) (! allow_execstack));
+# endif
#endif
return ! allow_execstack;
}
-static void
-deeper (void (*f) (void))
-{
- char stack[1100 * 1024];
- explicit_bzero (stack, sizeof stack);
- (*f) ();
- memfrob (stack, sizeof stack);
-}
-
-
#include <support/test-driver.c>
diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index f35a8369bd..8069d3e0ae 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -446,25 +446,6 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE);
-
- /* There might have been a race. Another thread might have
- caused the stacks to get exec permission while this new
- stack was prepared. Detect if this was possible and
- change the permission if necessary. */
- if (__builtin_expect ((GL(dl_stack_flags) & PF_X) != 0
- && (prot & PROT_EXEC) == 0, 0))
- {
- int err = __nptl_change_stack_perm (pd);
- if (err != 0)
- {
- /* Free the stack memory we just allocated. */
- (void) __munmap (mem, size);
-
- return err;
- }
- }
-
-
/* Note that all of the stack and the thread descriptor is
zeroed. This means we do not have to initialize fields
with initial value zero. This is specifically true for
diff --git a/sysdeps/nptl/pthreadP.h b/sysdeps/nptl/pthreadP.h
index 30e8a2d177..79af27449a 100644
--- a/sysdeps/nptl/pthreadP.h
+++ b/sysdeps/nptl/pthreadP.h
@@ -280,12 +280,6 @@ __do_cancel (void)
extern void __nptl_free_tcb (struct pthread *pd);
libc_hidden_proto (__nptl_free_tcb)
-/* Change the permissions of a thread stack. Called from
- _dl_make_stacks_executable and pthread_create. */
-int
-__nptl_change_stack_perm (struct pthread *pd);
-rtld_hidden_proto (__nptl_change_stack_perm)
-
/* longjmp handling. */
extern void __pthread_cleanup_upto (__jmp_buf target, char *targetframe);
libc_hidden_proto (__pthread_cleanup_upto)
diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions
index 268ba1b6ac..05297934d6 100644
--- a/sysdeps/unix/sysv/linux/Versions
+++ b/sysdeps/unix/sysv/linux/Versions
@@ -356,7 +356,4 @@ ld {
__rseq_offset;
__rseq_size;
}
- GLIBC_PRIVATE {
- __nptl_change_stack_perm;
- }
}
diff --git a/sysdeps/unix/sysv/linux/dl-execstack.c b/sysdeps/unix/sysv/linux/dl-execstack.c
index b986898598..0b71ffca6d 100644
--- a/sysdeps/unix/sysv/linux/dl-execstack.c
+++ b/sysdeps/unix/sysv/linux/dl-execstack.c
@@ -16,19 +16,10 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
-#include <errno.h>
#include <ldsodefs.h>
-#include <libintl.h>
-#include <list.h>
-#include <pthreadP.h>
-#include <stackinfo.h>
-#include <stdbool.h>
-#include <sys/mman.h>
-#include <sysdep.h>
-#include <unistd.h>
-static int
-make_main_stack_executable (void **stack_endp)
+int
+_dl_make_stacks_executable (void **stack_endp)
{
/* This gives us the highest/lowest page that needs to be changed. */
uintptr_t page = ((uintptr_t) *stack_endp
@@ -52,57 +43,3 @@ make_main_stack_executable (void **stack_endp)
return 0;
}
-
-int
-_dl_make_stacks_executable (void **stack_endp)
-{
- /* First the main thread's stack. */
- int err = make_main_stack_executable (stack_endp);
- if (err != 0)
- return err;
-
- lll_lock (GL (dl_stack_cache_lock), LLL_PRIVATE);
-
- list_t *runp;
- list_for_each (runp, &GL (dl_stack_used))
- {
- err = __nptl_change_stack_perm (list_entry (runp, struct pthread, list));
- if (err != 0)
- break;
- }
-
- /* Also change the permission for the currently unused stacks. This
- might be wasted time but better spend it here than adding a check
- in the fast path. */
- if (err == 0)
- list_for_each (runp, &GL (dl_stack_cache))
- {
- err = __nptl_change_stack_perm (list_entry (runp, struct pthread,
- list));
- if (err != 0)
- break;
- }
-
- lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE);
-
- return err;
-}
-
-int
-__nptl_change_stack_perm (struct pthread *pd)
-{
-#if _STACK_GROWS_DOWN
- void *stack = pd->stackblock + pd->guardsize;
- size_t len = pd->stackblock_size - pd->guardsize;
-#elif _STACK_GROWS_UP
- void *stack = pd->stackblock;
- size_t len = (uintptr_t) pd - pd->guardsize - (uintptr_t) pd->stackblock;
-#else
-# error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
-#endif
- if (__mprotect (stack, len, PROT_READ | PROT_WRITE | PROT_EXEC) != 0)
- return errno;
-
- return 0;
-}
-rtld_hidden_def (__nptl_change_stack_perm)
diff --git a/sysdeps/unix/sysv/linux/mips/Makefile b/sysdeps/unix/sysv/linux/mips/Makefile
index d5725c69d8..05ec9150b2 100644
--- a/sysdeps/unix/sysv/linux/mips/Makefile
+++ b/sysdeps/unix/sysv/linux/mips/Makefile
@@ -61,6 +61,7 @@ ifeq ($(subdir),elf)
# this test is expected to fail.
ifneq ($(mips-has-gnustack),yes)
test-xfail-check-execstack = yes
+CFLAGS-tst-execstack.c += -DDEFAULT_RWX_STACK=1
endif
endif
@@ -68,6 +69,12 @@ ifeq ($(subdir),stdlib)
gen-as-const-headers += ucontext_i.sym
endif
+ifeq ($(subdir),nptl)
+ifeq ($(mips-force-execstack),yes)
+CFLAGS-tst-execstack-threads.c += -DDEFAULT_RWX_STACK=1
+endif
+endif
+
ifeq ($(mips-force-execstack),yes)
CFLAGS-.o += -Wa,-execstack
CFLAGS-.os += -Wa,-execstack
--
2.43.0
^ permalink raw reply [flat|nested] 5+ messages in thread* [PATCH v3 3/4] elf: Add tst-execstack-prog-static
2024-06-18 19:40 [PATCH v3 0/4] Improve executable stack handling Adhemerval Zanella
2024-06-18 19:40 ` [PATCH v3 1/4] elf: Consolidate stackinfo.h Adhemerval Zanella
2024-06-18 19:40 ` [PATCH v3 2/4] elf: Do not change stack permission on dlopen/dlmopen Adhemerval Zanella
@ 2024-06-18 19:40 ` Adhemerval Zanella
2024-06-18 19:40 ` [PATCH v3 4/4] elf: Add glibc.rtld.execstack Adhemerval Zanella
3 siblings, 0 replies; 5+ messages in thread
From: Adhemerval Zanella @ 2024-06-18 19:40 UTC (permalink / raw)
To: libc-alpha; +Cc: H . J . Lu, Florian Weimer, Zack Weinberg
Similar to tst-execstack-prog, check if executable stacks works for
statically linked programs.
---
elf/Makefile | 7 +++++++
elf/tst-execstack-prog-static.c | 1 +
2 files changed, 8 insertions(+)
create mode 100644 elf/tst-execstack-prog-static.c
diff --git a/elf/Makefile b/elf/Makefile
index bb6cd06dec..604b7df1cc 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -543,6 +543,9 @@ tests-execstack-yes = \
tst-execstack-needed \
tst-execstack-prog \
# tests-execstack-yes
+tests-execstack-static-yes = \
+ tst-execstack-prog-static
+ # tests-execstack-static-yes
endif
ifeq ($(have-depaudit),yes)
tests += \
@@ -630,6 +633,7 @@ $(objpfx)tst-rtld-does-not-exist.out: tst-rtld-does-not-exist.sh $(objpfx)ld.so
$(evaluate-test)
tests += $(tests-execstack-$(have-z-execstack))
+tests-static+= $(tests-execstack-static-$(have-z-execstack))
ifeq ($(run-built-tests),yes)
tests-special += \
$(objpfx)noload-mem.out \
@@ -1856,6 +1860,9 @@ LDFLAGS-tst-execstack-needed = -Wl,-z,noexecstack
LDFLAGS-tst-execstack-prog = -Wl,-z,execstack
CFLAGS-tst-execstack-prog.c += -Wno-trampolines
CFLAGS-tst-execstack-mod.c += -Wno-trampolines
+
+LDFLAGS-tst-execstack-prog-static = -Wl,-z,execstack
+CFLAGS-tst-execstack-prog-static.c += -Wno-trampolines
endif
LDFLAGS-tst-array2 = -Wl,--no-as-needed
diff --git a/elf/tst-execstack-prog-static.c b/elf/tst-execstack-prog-static.c
new file mode 100644
index 0000000000..328065dd9c
--- /dev/null
+++ b/elf/tst-execstack-prog-static.c
@@ -0,0 +1 @@
+#include <tst-execstack-prog.c>
--
2.43.0
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v3 4/4] elf: Add glibc.rtld.execstack
2024-06-18 19:40 [PATCH v3 0/4] Improve executable stack handling Adhemerval Zanella
` (2 preceding siblings ...)
2024-06-18 19:40 ` [PATCH v3 3/4] elf: Add tst-execstack-prog-static Adhemerval Zanella
@ 2024-06-18 19:40 ` Adhemerval Zanella
3 siblings, 0 replies; 5+ messages in thread
From: Adhemerval Zanella @ 2024-06-18 19:40 UTC (permalink / raw)
To: libc-alpha; +Cc: H . J . Lu, Florian Weimer, Zack Weinberg
The new tunable can be used to control whether executable stacks are
allowed from either the main program or dependencies. The default is
to allow executable stacks.
The executable stacks default permission is checked agains the one
provided by the PT_GNU_STACK from program headers (if present). The
tunable also disables the stack permission change if any dependency
requires an executable stack at loading time.
Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu.
---
NEWS | 4 ++++
elf/Makefile | 42 ++++++++++++++++++++++++++++++++++
elf/dl-load.c | 4 +++-
elf/dl-support.c | 5 ++++
elf/dl-tunables.list | 6 +++++
elf/rtld.c | 4 ++++
elf/tst-rtld-list-tunables.exp | 1 +
manual/tunables.texi | 19 +++++++++++++++
8 files changed, 84 insertions(+), 1 deletion(-)
diff --git a/NEWS b/NEWS
index 43ff2ee23b..a5bbf3851b 100644
--- a/NEWS
+++ b/NEWS
@@ -36,6 +36,10 @@ Major new features:
* On Linux, update epoll header to include epoll ioctl definitions and
related structure added in Linux kernel 6.9.
+* A new tunable, glibc.rtld.execstack, can be used to control whether
+ executable stacks are allowed from either main program or dependencies.
+ The default is to allow executable stacks.
+
Deprecated and removed features, and other changes affecting compatibility:
* Architectures which use a 32-bit seconds-since-epoch field in struct
diff --git a/elf/Makefile b/elf/Makefile
index 604b7df1cc..dba6a6ddac 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -546,6 +546,11 @@ tests-execstack-yes = \
tests-execstack-static-yes = \
tst-execstack-prog-static
# tests-execstack-static-yes
+tests-execstack-special-yes = \
+ $(objpfx)tst-execstack-prog-noexecstack.out \
+ $(objpfx)tst-execstack-needed-noexecstack.out \
+ $(objpfx)tst-execstack-prog-static-noexecstack.out \
+ # tests-execstack-special-yes
endif
ifeq ($(have-depaudit),yes)
tests += \
@@ -634,6 +639,7 @@ $(objpfx)tst-rtld-does-not-exist.out: tst-rtld-does-not-exist.sh $(objpfx)ld.so
tests += $(tests-execstack-$(have-z-execstack))
tests-static+= $(tests-execstack-static-$(have-z-execstack))
+tests-special += $(tests-execstack-special-$(have-z-execstack))
ifeq ($(run-built-tests),yes)
tests-special += \
$(objpfx)noload-mem.out \
@@ -1863,6 +1869,42 @@ CFLAGS-tst-execstack-mod.c += -Wno-trampolines
LDFLAGS-tst-execstack-prog-static = -Wl,-z,execstack
CFLAGS-tst-execstack-prog-static.c += -Wno-trampolines
+
+ifeq (yes,$(build-hardcoded-path-in-tests))
+tst-execstack-prog-noexecstack-msg = "Fatal glibc error: executable stack is not allowed$$"
+else
+tst-execstack-prog-noexecstack-msg = "error while loading shared libraries:.*cannot enable executable stack as shared object requires:"
+endif
+
+$(objpfx)tst-execstack-prog-noexecstack.out: $(objpfx)tst-execstack-prog
+ $(test-program-cmd-before-env) \
+ $(run-program-env) \
+ GLIBC_TUNABLES=glibc.rtld.execstack=0 \
+ $(test-program-cmd-after-env) $< \
+ > $@ 2>&1; echo "status: $$?" >> $@; \
+ grep -q $(tst-execstack-prog-noexecstack-msg) $@ \
+ && grep -q '^status: 127$$' $@; \
+ $(evaluate-test)
+
+$(objpfx)tst-execstack-needed-noexecstack.out: $(objpfx)tst-execstack-needed
+ $(test-program-cmd-before-env) \
+ $(run-program-env) \
+ GLIBC_TUNABLES=glibc.rtld.execstack=0 \
+ $(test-program-cmd-after-env) $< \
+ > $@ 2>&1; echo "status: $$?" >> $@; \
+ grep -q 'error while loading shared libraries:.*cannot enable executable stack as shared object requires:' $@ \
+ && grep -q '^status: 127$$' $@; \
+ $(evaluate-test)
+
+$(objpfx)tst-execstack-prog-static-noexecstack.out: $(objpfx)tst-execstack-prog-static
+ $(test-program-cmd-before-env) \
+ $(run-program-env) \
+ GLIBC_TUNABLES=glibc.rtld.execstack=0 \
+ $< \
+ > $@ 2>&1; echo "status: $$?" >> $@; \
+ grep -q 'Fatal glibc error: executable stack is not allowed$$' $@ \
+ && grep -q '^status: 127$$' $@; \
+ $(evaluate-test)
endif
LDFLAGS-tst-array2 = -Wl,--no-as-needed
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 015595aac4..75550fe089 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -32,6 +32,7 @@
#include <sys/stat.h>
#include <sys/types.h>
#include <gnu/lib-names.h>
+#include <dl-tunables.h>
/* Type for the buffer we put the ELF header and hopefully the program
header. This buffer does not really have to be too large. In most
@@ -1300,7 +1301,8 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
/* The stack is presently not executable, but this module
requires that it be executable. Only tries to change the
stack protection during process startup. */
- if ((mode & __RTLD_DLOPEN) == 0)
+ if ((mode & __RTLD_DLOPEN) == 0
+ && TUNABLE_GET (glibc, rtld, execstack, int32_t, NULL) == 1)
#if PTHREAD_IN_LIBC
errval = _dl_make_stacks_executable (stack_endp);
#else
diff --git a/elf/dl-support.c b/elf/dl-support.c
index 451932dd03..b674468572 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -45,6 +45,7 @@
#include <dl-find_object.h>
#include <array_length.h>
#include <dl-symbol-redir-ifunc.h>
+#include <dl-tunables.h>
extern char *__progname;
char **_dl_argv = &__progname; /* This is checked for some error messages. */
@@ -335,6 +336,10 @@ _dl_non_dynamic_init (void)
break;
}
+ if ((__glibc_unlikely (GL(dl_stack_flags)) & PF_X)
+ && TUNABLE_GET (glibc, rtld, execstack, int32_t, NULL) == 0)
+ _dl_fatal_printf ("Fatal glibc error: executable stack is not allowed\n");
+
call_function_static_weak (_dl_find_object_init);
/* Setup relro on the binary itself. */
diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list
index 1186272c81..2d6febc249 100644
--- a/elf/dl-tunables.list
+++ b/elf/dl-tunables.list
@@ -142,6 +142,12 @@ glibc {
maxval: 1
default: 0
}
+ execstack {
+ type: INT_32
+ minval: 0
+ maxval: 1
+ default: 1
+ }
}
mem {
diff --git a/elf/rtld.c b/elf/rtld.c
index e9525ea987..5793f291e4 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -1668,6 +1668,10 @@ dl_main (const ElfW(Phdr) *phdr,
bool has_interp = rtld_setup_main_map (main_map);
+ if ((__glibc_unlikely (GL(dl_stack_flags)) & PF_X)
+ && TUNABLE_GET (glibc, rtld, execstack, int32_t, NULL) == 0)
+ _dl_fatal_printf ("Fatal glibc error: executable stack is not allowed\n");
+
/* If the current libname is different from the SONAME, add the
latter as well. */
if (GL(dl_rtld_map).l_info[DT_SONAME] != NULL
diff --git a/elf/tst-rtld-list-tunables.exp b/elf/tst-rtld-list-tunables.exp
index db0e1c86e9..9f5990f340 100644
--- a/elf/tst-rtld-list-tunables.exp
+++ b/elf/tst-rtld-list-tunables.exp
@@ -13,5 +13,6 @@ glibc.malloc.top_pad: 0x20000 (min: 0x0, max: 0x[f]+)
glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0x[f]+)
glibc.rtld.dynamic_sort: 2 (min: 1, max: 2)
glibc.rtld.enable_secure: 0 (min: 0, max: 1)
+glibc.rtld.execstack: 1 (min: 0, max: 1)
glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
glibc.rtld.optional_static_tls: 0x200 (min: 0x0, max: 0x[f]+)
diff --git a/manual/tunables.texi b/manual/tunables.texi
index 8dd02d8149..f1674f31ea 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -356,6 +356,25 @@ tests for @code{AT_SECURE} programs and not meant to be a security feature.
The default value of this tunable is @samp{0}.
@end deftp
+@deftp Tunable glibc.rtld.execstack
+@theglibc{} will use either the default architecture flags (that might contain
+the executable bit) or the value of @code{PT_GNU_STACK} (if present), and if
+the program or any shared library dependency require an executable stack the
+loader will change the main stack permission if kernel starts with a non
+executable stack.
+
+The @code{glibc.rtld.execstack} tunable allows the user to control whether
+to control executable stacks from the main program or dependencies. Setting
+its value to @code{0} disable executable stacks, where @code{1} enables it.
+The default value is @code{1}.
+
+When executable stacks are not allowed, and if the main program or dependencies
+require an executable stack, the loader will fail with an error message.
+@strong{NB:} Trying to load a dynamic shared library with @code{dlopen} or
+@code{dlmopen} that requires an executable stack will always fail if the
+default flags does not contain the executable bit.
+@end deftp
+
@node Elision Tunables
@section Elision Tunables
@cindex elision tunables
--
2.43.0
^ permalink raw reply [flat|nested] 5+ messages in thread