From: nadav.amit@gmail.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 v6 03/24] x86/mm: Introduce temporary mm structs
Date: Fri, 26 Apr 2019 16:22:42 -0700 [thread overview]
Message-ID: <20190426232303.28381-4-nadav.amit@gmail.com> (raw)
In-Reply-To: <20190426232303.28381-1-nadav.amit@gmail.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 23:22 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-26 23:22 [PATCH v6 00/24] x86: text_poke() fixes and executable lockdowns nadav.amit
2019-04-26 23:22 ` [PATCH v6 01/24] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()" nadav.amit
2019-04-26 23:22 ` [PATCH v6 02/24] x86/jump_label: Use text_poke_early() during early init nadav.amit
2019-04-26 23:22 ` nadav.amit [this message]
2019-04-26 23:22 ` [PATCH v6 04/24] x86/mm: Save debug registers when loading a temporary mm nadav.amit
2019-04-26 23:22 ` [PATCH v6 05/24] uprobes: Initialize uprobes earlier nadav.amit
2019-04-26 23:22 ` [PATCH v6 06/24] fork: Provide a function for copying init_mm nadav.amit
2019-04-26 23:22 ` [PATCH v6 07/24] x86/alternative: Initialize temporary mm for patching nadav.amit
2019-04-26 23:22 ` [PATCH v6 08/24] x86/alternative: Use temporary mm for text poking nadav.amit
2019-04-26 23:22 ` [PATCH v6 09/24] x86/kgdb: Avoid redundant comparison of patched code nadav.amit
2019-04-26 23:22 ` [PATCH v6 10/24] x86/ftrace: Set trampoline pages as executable nadav.amit
2019-04-26 23:22 ` [PATCH v6 11/24] x86/kprobes: Set instruction page " nadav.amit
2019-04-26 23:22 ` [PATCH v6 12/24] x86/module: Avoid breaking W^X while loading modules nadav.amit
2019-04-26 23:22 ` [PATCH v6 13/24] x86/jump-label: Remove support for custom poker nadav.amit
2019-04-26 23:22 ` [PATCH v6 14/24] x86/alternative: Remove the return value of text_poke_*() nadav.amit
2019-04-26 23:22 ` [PATCH v6 15/24] x86/mm/cpa: Add set_direct_map_ functions nadav.amit
2019-04-26 23:22 ` [PATCH v6 16/24] mm: Make hibernate handle unmapped pages nadav.amit
2019-04-26 23:22 ` [PATCH v6 17/24] vmalloc: Add flag for free of special permsissions nadav.amit
2019-04-26 23:22 ` [PATCH v6 18/24] modules: Use vmalloc special flag nadav.amit
2019-04-26 23:22 ` [PATCH v6 19/24] bpf: " nadav.amit
2019-04-26 23:22 ` [PATCH v6 20/24] x86/ftrace: " nadav.amit
2019-04-26 23:23 ` [PATCH v6 21/24] x86/kprobes: " nadav.amit
2019-04-26 23:23 ` [PATCH v6 22/24] x86/alternative: Comment about module removal races nadav.amit
2019-04-26 23:23 ` [PATCH v6 23/24] mm/tlb: Provide default nmi_uaccess_okay() nadav.amit
2019-04-26 23:23 ` [PATCH v6 24/24] bpf: Fail bpf_probe_write_user() while mm is switched nadav.amit
2019-04-27 10:22 ` [PATCH v6 00/24] x86: text_poke() fixes and executable lockdowns Ingo Molnar
2019-04-27 10:32 ` Peter Zijlstra
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