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>,
Kees Cook <keescook@chromium.org>,
Dave Hansen <dave.hansen@intel.com>,
Nadav Amit <namit@vmware.com>
Subject: [PATCH v5 03/23] x86/mm: Introduce temporary mm structs
Date: Thu, 25 Apr 2019 17:11:23 -0700 [thread overview]
Message-ID: <20190426001143.4983-4-namit@vmware.com> (raw)
In-Reply-To: <20190426001143.4983-1-namit@vmware.com>
From: Andy Lutomirski <luto@kernel.org>
Using a dedicated page-table for temporary PTEs prevents other cores
from using - even speculatively - these PTEs, thereby providing two
benefits:
(1) Security hardening: an attacker that gains kernel memory writing
abilities cannot easily overwrite sensitive data.
(2) Avoiding TLB shootdowns: the PTEs do not need to be flushed in
remote page-tables.
To do so a temporary mm_struct can be used. Mappings which are private
for this mm can be set in the userspace part of the address-space.
During the whole time in which the temporary mm is loaded, interrupts
must be disabled.
The first use-case for temporary mm struct, which will follow, is for
poking the kernel text.
[ Commit message was written by Nadav Amit ]
Cc: Kees Cook <keescook@chromium.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
---
arch/x86/include/asm/mmu_context.h | 33 ++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 19d18fae6ec6..24dc3b810970 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -356,4 +356,37 @@ static inline unsigned long __get_current_cr3_fast(void)
return cr3;
}
+typedef struct {
+ struct mm_struct *mm;
+} temp_mm_state_t;
+
+/*
+ * Using a temporary mm allows to set temporary mappings that are not accessible
+ * by other CPUs. Such mappings are needed to perform sensitive memory writes
+ * that override the kernel memory protections (e.g., W^X), without exposing the
+ * temporary page-table mappings that are required for these write operations to
+ * other CPUs. Using a temporary mm also allows to avoid TLB shootdowns when the
+ * mapping is torn down.
+ *
+ * Context: The temporary mm needs to be used exclusively by a single core. To
+ * harden security IRQs must be disabled while the temporary mm is
+ * loaded, thereby preventing interrupt handler bugs from overriding
+ * the kernel memory protection.
+ */
+static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm)
+{
+ temp_mm_state_t temp_state;
+
+ lockdep_assert_irqs_disabled();
+ temp_state.mm = this_cpu_read(cpu_tlbstate.loaded_mm);
+ switch_mm_irqs_off(NULL, mm, current);
+ return temp_state;
+}
+
+static inline void unuse_temporary_mm(temp_mm_state_t prev_state)
+{
+ lockdep_assert_irqs_disabled();
+ switch_mm_irqs_off(NULL, prev_state.mm, current);
+}
+
#endif /* _ASM_X86_MMU_CONTEXT_H */
--
2.17.1
next prev parent reply other threads:[~2019-04-26 0:11 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 ` Nadav Amit [this message]
2019-04-30 11:16 ` [tip:x86/mm] x86/mm: Introduce temporary mm structs 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 ` [PATCH v5 11/23] x86/module: Avoid breaking W^X while loading modules Nadav Amit
2019-04-30 11:22 ` [tip:x86/mm] x86/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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