From: Rick Edgecombe <rick.p.edgecombe@intel.com>
To: 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>,
Borislav Petkov <bp@alien8.de>, Nadav Amit <nadav.amit@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
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,
Kees Cook <keescook@chromium.org>,
Dave Hansen <dave.hansen@intel.com>,
Nadav Amit <namit@vmware.com>,
Rick Edgecombe <rick.p.edgecombe@intel.com>
Subject: [PATCH v3 02/20] x86/mm: Introduce temporary mm structs
Date: Thu, 21 Feb 2019 15:44:33 -0800 [thread overview]
Message-ID: <20190221234451.17632-3-rick.p.edgecombe@intel.com> (raw)
In-Reply-To: <20190221234451.17632-1-rick.p.edgecombe@intel.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..d684b954f3c0 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 *prev;
+} temp_mm_state_t;
+
+/*
+ * Using a temporary mm allows to set temporary mappings that are not accessible
+ * by other cores. 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 cores. Using 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 state;
+
+ lockdep_assert_irqs_disabled();
+ state.prev = this_cpu_read(cpu_tlbstate.loaded_mm);
+ switch_mm_irqs_off(NULL, mm, current);
+ return state;
+}
+
+static inline void unuse_temporary_mm(temp_mm_state_t prev)
+{
+ lockdep_assert_irqs_disabled();
+ switch_mm_irqs_off(NULL, prev.prev, current);
+}
+
#endif /* _ASM_X86_MMU_CONTEXT_H */
--
2.17.1
next prev parent reply other threads:[~2019-02-21 23:52 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-21 23:44 [PATCH v3 00/20] Merge text_poke fixes and executable lockdowns Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 01/20] x86/jump_label: Use text_poke_early() during early init Rick Edgecombe
2019-02-21 23:44 ` Rick Edgecombe [this message]
2019-02-21 23:44 ` [PATCH v3 03/20] x86/mm: Save DRs when loading a temporary mm Rick Edgecombe
2019-02-22 0:07 ` Sean Christopherson
2019-02-22 0:17 ` Nadav Amit
2019-02-21 23:44 ` [PATCH v3 04/20] fork: Provide a function for copying init_mm Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 05/20] x86/alternative: Initialize temporary mm for patching Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 06/20] x86/alternative: Use temporary mm for text poking Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 07/20] x86/kgdb: Avoid redundant comparison of patched code Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 08/20] x86/ftrace: Set trampoline pages as executable Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 09/20] x86/kprobes: Set instruction page " Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 10/20] x86/module: Avoid breaking W^X while loading modules Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 11/20] x86/jump-label: Remove support for custom poker Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 12/20] x86/alternative: Remove the return value of text_poke_*() Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 13/20] x86/mm/cpa: Add set_direct_map_ functions Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 14/20] mm: Make hibernate handle unmapped pages Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 15/20] vmalloc: Add flag for free of special permsissions Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 16/20] modules: Use vmalloc special flag Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 17/20] bpf: " Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 18/20] x86/ftrace: " Rick Edgecombe
2019-02-22 0:22 ` Steven Rostedt
2019-02-22 0:55 ` Edgecombe, Rick P
2019-02-21 23:44 ` [PATCH v3 19/20] x86/kprobes: " Rick Edgecombe
2019-02-21 23:44 ` [PATCH v3 20/20] x86/alternative: Comment about module removal races Rick Edgecombe
2019-02-22 16:14 ` [PATCH v3 00/20] Merge text_poke fixes and executable lockdowns Borislav Petkov
2019-02-22 18:32 ` Edgecombe, Rick P
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