From: Nadav Amit <namit@vmware.com>
To: Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
Ingo Molnar <mingo@redhat.com>
Cc: <linux-kernel@vger.kernel.org>, <x86@kernel.org>, <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Nadav Amit <nadav.amit@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>, <linux_dti@icloud.com>,
<linux-integrity@vger.kernel.org>,
<linux-security-module@vger.kernel.org>,
<akpm@linux-foundation.org>,
<kernel-hardening@lists.openwall.com>, <linux-mm@kvack.org>,
<will.deacon@arm.com>, <ard.biesheuvel@linaro.org>,
<kristen@linux.intel.com>, <deneen.t.dock@intel.com>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
Nadav Amit <namit@vmware.com>, Kees Cook <keescook@chromium.org>,
Dave Hansen <dave.hansen@intel.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Jessica Yu <jeyu@kernel.org>
Subject: [PATCH v5 11/23] x86/module: Avoid breaking W^X while loading modules
Date: Thu, 25 Apr 2019 17:11:31 -0700 [thread overview]
Message-ID: <20190426001143.4983-12-namit@vmware.com> (raw)
In-Reply-To: <20190426001143.4983-1-namit@vmware.com>
When modules and BPF filters are loaded, there is a time window in
which some memory is both writable and executable. An attacker that has
already found another vulnerability (e.g., a dangling pointer) might be
able to exploit this behavior to overwrite kernel code. Prevent having
writable executable PTEs in this stage.
In addition, avoiding having W+X mappings can also slightly simplify the
patching of modules code on initialization (e.g., by alternatives and
static-key), as would be done in the next patch. This was actually the
main motivation for this patch.
To avoid having W+X mappings, set them initially as RW (NX) and after
they are set as RO set them as X as well. Setting them as executable is
done as a separate step to avoid one core in which the old PTE is cached
(hence writable), and another which sees the updated PTE (executable),
which would break the W^X protection.
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jessica Yu <jeyu@kernel.org>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Suggested-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
---
arch/x86/kernel/alternative.c | 28 +++++++++++++++++++++-------
arch/x86/kernel/module.c | 2 +-
include/linux/filter.h | 1 +
kernel/module.c | 5 +++++
4 files changed, 28 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 599203876c32..3d2b6b6fb20c 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -668,15 +668,29 @@ void __init alternative_instructions(void)
* handlers seeing an inconsistent instruction while you patch.
*/
void *__init_or_module text_poke_early(void *addr, const void *opcode,
- size_t len)
+ size_t len)
{
unsigned long flags;
- local_irq_save(flags);
- memcpy(addr, opcode, len);
- local_irq_restore(flags);
- sync_core();
- /* Could also do a CLFLUSH here to speed up CPU recovery; but
- that causes hangs on some VIA CPUs. */
+
+ if (boot_cpu_has(X86_FEATURE_NX) &&
+ is_module_text_address((unsigned long)addr)) {
+ /*
+ * Modules text is marked initially as non-executable, so the
+ * code cannot be running and speculative code-fetches are
+ * prevented. Just change the code.
+ */
+ memcpy(addr, opcode, len);
+ } else {
+ local_irq_save(flags);
+ memcpy(addr, opcode, len);
+ local_irq_restore(flags);
+ sync_core();
+
+ /*
+ * Could also do a CLFLUSH here to speed up CPU recovery; but
+ * that causes hangs on some VIA CPUs.
+ */
+ }
return addr;
}
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index b052e883dd8c..cfa3106faee4 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -87,7 +87,7 @@ void *module_alloc(unsigned long size)
p = __vmalloc_node_range(size, MODULE_ALIGN,
MODULES_VADDR + get_module_load_offset(),
MODULES_END, GFP_KERNEL,
- PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
+ PAGE_KERNEL, 0, NUMA_NO_NODE,
__builtin_return_address(0));
if (p && (kasan_module_alloc(p, size) < 0)) {
vfree(p);
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 6074aa064b54..14ec3bdad9a9 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -746,6 +746,7 @@ static inline void bpf_prog_unlock_ro(struct bpf_prog *fp)
static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)
{
set_memory_ro((unsigned long)hdr, hdr->pages);
+ set_memory_x((unsigned long)hdr, hdr->pages);
}
static inline void bpf_jit_binary_unlock_ro(struct bpf_binary_header *hdr)
diff --git a/kernel/module.c b/kernel/module.c
index 0b9aa8ab89f0..2b2845ae983e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1950,8 +1950,13 @@ void module_enable_ro(const struct module *mod, bool after_init)
return;
frob_text(&mod->core_layout, set_memory_ro);
+ frob_text(&mod->core_layout, set_memory_x);
+
frob_rodata(&mod->core_layout, set_memory_ro);
+
frob_text(&mod->init_layout, set_memory_ro);
+ frob_text(&mod->init_layout, set_memory_x);
+
frob_rodata(&mod->init_layout, set_memory_ro);
if (after_init)
--
2.17.1
next prev parent reply other threads:[~2019-04-26 7:31 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-26 0:11 [PATCH v5 00/23] x86: text_poke() fixes and executable lockdowns Nadav Amit
2019-04-26 0:11 ` [PATCH v5 01/23] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()" Nadav Amit
2019-04-30 11:13 ` [tip:x86/mm] x86/alternatives: Add text_poke_kgdb() to not assert the lock when debugging tip-bot for Nadav Amit
2019-04-26 0:11 ` [PATCH v5 02/23] x86/jump_label: Use text_poke_early() during early init Nadav Amit
2019-04-30 11:15 ` [tip:x86/mm] " tip-bot for Nadav Amit
2019-04-26 0:11 ` [PATCH v5 03/23] x86/mm: Introduce temporary mm structs Nadav Amit
2019-04-30 11:16 ` [tip:x86/mm] " tip-bot for Andy Lutomirski
2019-04-26 0:11 ` [PATCH v5 04/23] x86/mm: Save debug registers when loading a temporary mm Nadav Amit
2019-04-30 11:17 ` [tip:x86/mm] " tip-bot for Nadav Amit
2019-04-26 0:11 ` [PATCH v5 05/23] fork: Provide a function for copying init_mm Nadav Amit
2019-04-30 11:18 ` [tip:x86/mm] " tip-bot for Nadav Amit
2019-04-26 0:11 ` [PATCH v5 06/23] x86/alternative: Initialize temporary mm for patching Nadav Amit
2019-04-26 0:11 ` [PATCH v5 07/23] x86/alternative: Use temporary mm for text poking Nadav Amit
2019-04-30 11:20 ` [tip:x86/mm] x86/alternatives: " tip-bot for Nadav Amit
2019-04-26 0:11 ` [PATCH v5 08/23] x86/kgdb: Avoid redundant comparison of patched code Nadav Amit
2019-04-30 11:20 ` [tip:x86/mm] " tip-bot for Nadav Amit
2019-04-26 0:11 ` [PATCH v5 09/23] x86/ftrace: Set trampoline pages as executable Nadav Amit
2019-04-30 11:21 ` [tip:x86/mm] " tip-bot for Nadav Amit
2019-04-26 0:11 ` [PATCH v5 10/23] x86/kprobes: Set instruction page " Nadav Amit
2019-04-30 11:22 ` [tip:x86/mm] " tip-bot for Nadav Amit
2019-04-26 0:11 ` Nadav Amit [this message]
2019-04-30 11:22 ` [tip:x86/mm] x86/modules: Avoid breaking W^X while loading modules tip-bot for Nadav Amit
2019-04-26 0:11 ` [PATCH v5 12/23] x86/jump-label: Remove support for custom poker Nadav Amit
2019-04-30 11:23 ` [tip:x86/mm] x86/jump-label: Remove support for custom text poker tip-bot for Nadav Amit
2019-04-26 0:11 ` [PATCH v5 13/23] x86/alternative: Remove the return value of text_poke_*() Nadav Amit
2019-04-30 11:24 ` [tip:x86/mm] x86/alternatives: " tip-bot for Nadav Amit
2019-04-26 0:11 ` [PATCH v5 14/23] x86/mm/cpa: Add set_direct_map_ functions Nadav Amit
2019-04-26 16:40 ` Linus Torvalds
2019-04-26 16:43 ` Nadav Amit
2019-04-30 11:24 ` [tip:x86/mm] x86/mm/cpa: Add set_direct_map_*() functions tip-bot for Rick Edgecombe
2019-04-26 0:11 ` [PATCH v5 15/23] mm: Make hibernate handle unmapped pages Nadav Amit
2019-04-30 11:25 ` [tip:x86/mm] mm/hibernation: Make hibernation " tip-bot for Rick Edgecombe
2019-04-26 0:11 ` [PATCH v5 16/23] vmalloc: Add flag for free of special permsissions Nadav Amit
2019-04-30 11:26 ` [tip:x86/mm] mm/vmalloc: Add flag for freeing " tip-bot for Rick Edgecombe
2019-04-26 0:11 ` [PATCH v5 17/23] modules: Use vmalloc special flag Nadav Amit
2019-04-30 11:26 ` [tip:x86/mm] " tip-bot for Rick Edgecombe
2019-04-26 0:11 ` [PATCH v5 18/23] bpf: " Nadav Amit
2019-04-30 11:27 ` [tip:x86/mm] " tip-bot for Rick Edgecombe
2019-04-26 0:11 ` [PATCH v5 19/23] x86/ftrace: " Nadav Amit
2019-04-30 11:28 ` [tip:x86/mm] " tip-bot for Rick Edgecombe
2019-04-26 0:11 ` [PATCH v5 20/23] x86/kprobes: " Nadav Amit
2019-04-30 11:28 ` [tip:x86/mm] " tip-bot for Rick Edgecombe
2019-04-26 0:11 ` [PATCH v5 21/23] x86/alternative: Comment about module removal races Nadav Amit
2019-04-30 11:29 ` [tip:x86/mm] x86/alternatives: Add comment " tip-bot for Nadav Amit
2019-04-26 0:11 ` [PATCH v5 22/23] mm/tlb: Provide default nmi_uaccess_okay() Nadav Amit
2019-04-30 11:14 ` [tip:x86/mm] " tip-bot for Nadav Amit
2019-04-26 0:11 ` [PATCH v5 23/23] bpf: Fail bpf_probe_write_user() while mm is switched Nadav Amit
2019-04-30 11:15 ` [tip:x86/mm] " tip-bot for Nadav Amit
2019-04-26 12:36 ` [PATCH v5 00/23] x86: text_poke() fixes and executable lockdowns Peter Zijlstra
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