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>
Subject: [PATCH v5 04/23] x86/mm: Save debug registers when loading a temporary mm
Date: Thu, 25 Apr 2019 17:11:24 -0700 [thread overview]
Message-ID: <20190426001143.4983-5-namit@vmware.com> (raw)
In-Reply-To: <20190426001143.4983-1-namit@vmware.com>
Prevent user watchpoints from mistakenly firing while the temporary mm
is being used. As the addresses of the temporary mm might overlap those
of the user-process, this is necessary to prevent wrong signals or worse
things from happening.
Cc: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.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 | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 24dc3b810970..93dff1963337 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -13,6 +13,7 @@
#include <asm/tlbflush.h>
#include <asm/paravirt.h>
#include <asm/mpx.h>
+#include <asm/debugreg.h>
extern atomic64_t last_mm_ctx_id;
@@ -380,6 +381,21 @@ static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm)
lockdep_assert_irqs_disabled();
temp_state.mm = this_cpu_read(cpu_tlbstate.loaded_mm);
switch_mm_irqs_off(NULL, mm, current);
+
+ /*
+ * If breakpoints are enabled, disable them while the temporary mm is
+ * used. Userspace might set up watchpoints on addresses that are used
+ * in the temporary mm, which would lead to wrong signals being sent or
+ * crashes.
+ *
+ * Note that breakpoints are not disabled selectively, which also causes
+ * kernel breakpoints (e.g., perf's) to be disabled. This might be
+ * undesirable, but still seems reasonable as the code that runs in the
+ * temporary mm should be short.
+ */
+ if (hw_breakpoint_active())
+ hw_breakpoint_disable();
+
return temp_state;
}
@@ -387,6 +403,13 @@ 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);
+
+ /*
+ * Restore the breakpoints if they were disabled before the temporary mm
+ * was loaded.
+ */
+ if (hw_breakpoint_active())
+ hw_breakpoint_restore();
}
#endif /* _ASM_X86_MMU_CONTEXT_H */
--
2.17.1
next prev parent reply other threads:[~2019-04-26 7:33 UTC|newest]
Thread overview: 27+ 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
2019-04-26 0:11 ` [PATCH v5 02/23] x86/jump_label: Use text_poke_early() during early init Nadav Amit
2019-04-26 0:11 ` [PATCH v5 03/23] x86/mm: Introduce temporary mm structs Nadav Amit
2019-04-26 0:11 ` Nadav Amit [this message]
2019-04-26 0:11 ` [PATCH v5 05/23] fork: Provide a function for copying init_mm 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
2019-04-26 0:11 ` [PATCH v5 08/23] x86/kgdb: Avoid redundant comparison of patched code Nadav Amit
2019-04-26 0:11 ` [PATCH v5 09/23] x86/ftrace: Set trampoline pages as executable Nadav Amit
2019-04-26 0:11 ` [PATCH v5 10/23] x86/kprobes: Set instruction page " Nadav Amit
2019-04-26 0:11 ` [PATCH v5 11/23] x86/module: Avoid breaking W^X while loading modules Nadav Amit
2019-04-26 0:11 ` [PATCH v5 12/23] x86/jump-label: Remove support for custom poker Nadav Amit
2019-04-26 0:11 ` [PATCH v5 13/23] x86/alternative: Remove the return value of text_poke_*() 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
2019-04-26 0:11 ` [PATCH v5 15/23] mm: Make hibernate handle unmapped pages Nadav Amit
2019-04-26 0:11 ` [PATCH v5 16/23] vmalloc: Add flag for free of special permsissions Nadav Amit
2019-04-26 0:11 ` [PATCH v5 17/23] modules: Use vmalloc special flag Nadav Amit
2019-04-26 0:11 ` [PATCH v5 18/23] bpf: " Nadav Amit
2019-04-26 0:11 ` [PATCH v5 19/23] x86/ftrace: " Nadav Amit
2019-04-26 0:11 ` [PATCH v5 20/23] x86/kprobes: " Nadav Amit
2019-04-26 0:11 ` [PATCH v5 21/23] x86/alternative: Comment about module removal races Nadav Amit
2019-04-26 0:11 ` [PATCH v5 22/23] mm/tlb: Provide default nmi_uaccess_okay() Nadav Amit
2019-04-26 0:11 ` [PATCH v5 23/23] bpf: Fail bpf_probe_write_user() while mm is switched Nadav Amit
2019-04-26 12:36 ` [PATCH v5 00/23] x86: text_poke() fixes and executable lockdowns Peter Zijlstra
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