From: Dan Williams <dan.j.williams@intel.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>,
Luis Henriques <lhenriques@suse.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
Kernel Hardening <kernel-hardening@lists.openwall.com>,
Greg KH <gregkh@linuxfoundation.org>, X86 ML <x86@kernel.org>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
Alan Cox <alan@linux.intel.com>
Subject: Re: [PATCH v4 07/10] x86: narrow out of bounds syscalls to sys_read under speculation
Date: Tue, 6 Feb 2018 13:37:27 -0800 [thread overview]
Message-ID: <CAPcyv4hELJQMEBQ_gi+_bh4D=7h47ypzK++XTdQjhDGnOs2uRg@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFy2-OMMCatHTXL7wfP7H=4CEKv4Y_pRvfeEOCwxriDP4Q@mail.gmail.com>
On Tue, Feb 6, 2018 at 12:58 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Tue, Feb 6, 2018 at 12:49 PM, Andy Lutomirski <luto@kernel.org> wrote:
>>
>> Can you use @cc to make an asm statement that outputs both the masked
>> array index and the "if" condition? I can never remember the syntax,
>> but something like:
>
> Yes. Although I'd actually suggest just using an "asm goto" if we
> really want to optimize this. Give the "index_mask_nospec()" a third
> argument that is the label to jump to for overflow.
>
> Then you can just decide how to implement it best for any particular
> architecture (and compiler limitation).
At that point we're basically just back to the array_ptr() version
that returned a sanitized pointer to an array element.
call = array_ptr(sys_call_table, nr & __SYSCALL_MASK, NR_syscalls);
if (likely(call))
regs->ax = (*call)(
regs->di, regs->si, regs->dx,
regs->r10, regs->r8, regs->r9);
e1e: ba 4d 01 00 00 mov $0x14d,%edx
e23: 48 39 d5 cmp %rdx,%rbp
e26: 48 19 d2 sbb %rdx,%rdx
call = array_ptr(sys_call_table, nr & __SYSCALL_MASK, NR_syscalls);
e29: 48 21 d5 and %rdx,%rbp
e2c: 48 8d 04 ed 00 00 00 lea 0x0(,%rbp,8),%rax
e33: 00
if (likely(call))
e34: 48 21 d0 and %rdx,%rax
e37: 74 1e je e57 <do_syscall_64+0x77>
regs->ax = (*call)(
e39: 48 8b 4b 38 mov 0x38(%rbx),%rcx
e3d: 48 8b 53 60 mov 0x60(%rbx),%rdx
e41: 48 8b 73 68 mov 0x68(%rbx),%rsi
e45: 48 8b 7b 70 mov 0x70(%rbx),%rdi
e49: 4c 8b 4b 40 mov 0x40(%rbx),%r9
e4d: 4c 8b 43 48 mov 0x48(%rbx),%r8
e51: ff 10 callq *(%rax)
e53: 48 89 43 50 mov %rax,0x50(%rbx)
e57: 65 48 8b 04 25 00 00 mov %gs:0x0,%rax
next prev parent reply other threads:[~2018-02-06 21:37 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-19 0:01 [PATCH v4 00/10] prevent bounds-check bypass via speculative execution Dan Williams
2018-01-19 0:01 ` [kernel-hardening] " Dan Williams
2018-01-19 0:01 ` Dan Williams
2018-01-19 0:01 ` [PATCH v4 01/10] Documentation: document array_ptr Dan Williams
2018-01-19 0:01 ` [kernel-hardening] " Dan Williams
2018-01-19 0:01 ` [PATCH v4 02/10] asm/nospec, array_ptr: sanitize speculative array de-references Dan Williams
2018-01-19 0:01 ` [kernel-hardening] " Dan Williams
2018-01-19 10:20 ` Jann Horn
2018-01-19 17:48 ` Adam Sampson
2018-01-19 17:48 ` Adam Sampson
2018-01-19 17:48 ` Adam Sampson
2018-01-19 17:48 ` Adam Sampson
2018-01-19 18:12 ` Dan Williams
2018-01-19 18:18 ` Will Deacon
2018-01-19 18:18 ` Will Deacon
2018-01-19 18:26 ` [kernel-hardening] " Dan Williams
2018-01-19 18:18 ` Linus Torvalds
2018-01-19 18:18 ` Linus Torvalds
2018-01-19 20:55 ` [kernel-hardening] " Dan Williams
2018-01-25 7:09 ` Cyril Novikov
2018-01-25 7:09 ` [kernel-hardening] " Cyril Novikov
2018-01-25 22:37 ` Dan Williams
2018-01-25 22:37 ` [kernel-hardening] " Dan Williams
2018-01-19 0:01 ` [PATCH v4 03/10] x86: implement array_ptr_mask() Dan Williams
2018-01-19 0:01 ` [kernel-hardening] " Dan Williams
2018-01-19 0:01 ` [PATCH v4 04/10] x86: introduce __uaccess_begin_nospec and ifence Dan Williams
2018-01-19 0:01 ` [kernel-hardening] " Dan Williams
2018-01-19 0:02 ` [PATCH v4 05/10] x86, __get_user: use __uaccess_begin_nospec Dan Williams
2018-01-19 0:02 ` [kernel-hardening] " Dan Williams
2018-01-19 0:02 ` [PATCH v4 06/10] x86, get_user: use pointer masking to limit speculation Dan Williams
2018-01-19 0:02 ` [kernel-hardening] " Dan Williams
2018-01-19 0:02 ` [PATCH v4 07/10] x86: narrow out of bounds syscalls to sys_read under speculation Dan Williams
2018-01-19 0:02 ` [kernel-hardening] " Dan Williams
2018-01-24 14:40 ` Jiri Slaby
2018-01-24 14:40 ` [kernel-hardening] " Jiri Slaby
2018-02-06 19:29 ` Luis Henriques
2018-02-06 19:48 ` Dan Williams
2018-02-06 20:26 ` Linus Torvalds
2018-02-06 20:37 ` Dan Williams
2018-02-06 20:42 ` Linus Torvalds
2018-02-06 20:43 ` Linus Torvalds
2018-02-06 20:49 ` Andy Lutomirski
2018-02-06 20:58 ` Linus Torvalds
2018-02-06 21:37 ` Dan Williams [this message]
2018-02-06 22:52 ` Linus Torvalds
2018-02-07 0:33 ` Dan Williams
2018-02-07 1:23 ` Linus Torvalds
2018-02-06 22:51 ` Luis Henriques
2018-02-06 22:51 ` Luis Henriques
2018-01-19 0:02 ` [PATCH v4 08/10] vfs, fdtable: prevent bounds-check bypass via speculative execution Dan Williams
2018-01-19 0:02 ` [kernel-hardening] " Dan Williams
2018-01-19 0:02 ` [PATCH v4 09/10] kvm, x86: fix spectre-v1 mitigation Dan Williams
2018-01-19 0:02 ` [kernel-hardening] " Dan Williams
2018-01-19 8:42 ` Paolo Bonzini
2018-01-19 8:42 ` [kernel-hardening] " Paolo Bonzini
2018-01-19 0:02 ` [PATCH v4 10/10] nl80211: sanitize array index in parse_txq_params Dan Williams
2018-01-19 0:02 ` [kernel-hardening] " Dan Williams
2018-01-19 0:02 ` Dan Williams
2018-01-21 10:37 ` Johannes Berg
2018-01-21 10:37 ` [kernel-hardening] " Johannes Berg
2018-01-21 10:37 ` Johannes Berg
2018-01-20 6:58 ` [PATCH v4 00/10] prevent bounds-check bypass via speculative execution Dan Williams
2018-01-20 6:58 ` [kernel-hardening] " Dan Williams
2018-01-20 6:58 ` Dan Williams
2018-01-20 16:56 ` Alexei Starovoitov
2018-01-20 16:56 ` [kernel-hardening] " Alexei Starovoitov
2018-01-20 16:56 ` Alexei Starovoitov
2018-01-20 17:07 ` Alexei Starovoitov
2018-01-20 17:07 ` [kernel-hardening] " Alexei Starovoitov
2018-01-20 17:07 ` Alexei Starovoitov
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