lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Thu, 30 Aug 2018 10:32:14 -0700 From: Nadav Amit <namit@...are.com> To: Thomas Gleixner <tglx@...utronix.de> CC: <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...hat.com>, <x86@...nel.org>, Arnd Bergmann <arnd@...db.de>, <linux-arch@...r.kernel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, Andy Lutomirski <luto@...nel.org>, Masami Hiramatsu <mhiramat@...nel.org>, Kees Cook <keescook@...omium.org>, Peter Zijlstra <peterz@...radead.org>, Dave Hansen <dave.hansen@...el.com>, Nadav Amit <namit@...are.com> Subject: [PATCH 2/6] x86/mm: temporary mm struct From: Andy Lutomirski <luto@...nel.org> Sometimes we want to set a temporary page-table entries (PTEs) in one of the cores, without allowing other cores to use - even speculatively - these mappings. There are two benefits for doing so: (1) Security: if sensitive PTEs are set, temporary mm prevents their use in other cores. This hardens the security as it prevents exploding a dangling pointer to overwrite sensitive data using the sensitive PTE. (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 PTEs, which will follow, is for poking the kernel text. [ Commit message was written by Nadav ] Cc: Masami Hiramatsu <mhiramat@...nel.org> Cc: Kees Cook <keescook@...omium.org> Cc: Peter Zijlstra <peterz@...radead.org> Cc: Dave Hansen <dave.hansen@...el.com> Signed-off-by: Andy Lutomirski <luto@...nel.org> Signed-off-by: Nadav Amit <namit@...are.com> --- arch/x86/include/asm/mmu_context.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index eeeb9289c764..96afc8c0cf15 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -338,4 +338,24 @@ static inline unsigned long __get_current_cr3_fast(void) return cr3; } +typedef struct { + struct mm_struct *prev; +} temporary_mm_state_t; + +static inline temporary_mm_state_t use_temporary_mm(struct mm_struct *mm) +{ + temporary_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(temporary_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
Powered by blists - more mailing lists