Date: Thu, 18 Jan 2018 16:01:36 -0800 From: Dan Williams <dan.j.williams@...el.com> To: linux-kernel@...r.kernel.org Cc: Mark Rutland <mark.rutland@....com>, kernel-hardening@...ts.openwall.com, Peter Zijlstra <peterz@...radead.org>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, "H. Peter Anvin" <hpa@...or.com>, Elena Reshetova <elena.reshetova@...el.com>, linux-arch@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>, Jonathan Corbet <corbet@....net>, x86@...nel.org, Russell King <linux@...linux.org.uk>, Ingo Molnar <mingo@...hat.com>, Andrew Honig <ahonig@...gle.com>, alan@...ux.intel.com, Tom Lendacky <thomas.lendacky@....com>, Kees Cook <keescook@...omium.org>, Al Viro <viro@...iv.linux.org.uk>, Andy Lutomirski <luto@...nel.org>, tglx@...utronix.de, akpm@...ux-foundation.org, Jim Mattson <jmattson@...gle.com>, Christian Lamparter <chunkeey@...il.com>, gregkh@...uxfoundation.org, linux-wireless@...r.kernel.org, stable@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>, Johannes Berg <johannes@...solutions.net>, torvalds@...ux-foundation.org, "David S. Miller" <davem@...emloft.net> Subject: [PATCH v4 00/10] prevent bounds-check bypass via speculative execution Changes since v3  * Drop 'ifence_array_ptr' and associated compile-time + run-time switching and just use the masking approach all the time. * Convert 'get_user' to use pointer sanitization via masking rather than lfence. '__get_user' and associated paths still rely on lfence. (Linus) "Basically, the rule is trivial: find all 'stac' users, and use address masking if those users already integrate the limit check, and lfence they don't." * At syscall entry sanitize the syscall number under speculation to remove a user controlled pointer de-reference in kernel space. (Linus) * Fix a raw lfence in the kvm code (added for v4.15-rc8) to use 'array_ptr'. * Propose 'array_idx' as a way to sanitize user input that is later used as an array index, but where the validation is happening in a different code block than the array reference. (Christian). * Fix grammar in speculation.txt (Kees) --- Quoting Mark's original RFC: "Recently, Google Project Zero discovered several classes of attack against speculative execution. One of these, known as variant-1, allows explicit bounds checks to be bypassed under speculation, providing an arbitrary read gadget. Further details can be found on the GPZ blog  and the Documentation patch in this series." A precondition of using this attack on the kernel is to get a user controlled pointer de-referenced (under speculation) in privileged code. The primary source of user controlled pointers in the kernel is the arguments passed to 'get_user' and '__get_user'. An example of other user controlled pointers are user-controlled array / pointer offsets. Better tooling is needed to find more arrays / pointers with user controlled indices / offsets that can be converted to use 'array_ptr' or 'array_idx'. A few are included in this set, and these are not expected to be complete. That said, the 'get_user' protections raise the bar on finding a vulnerable gadget in the kernel. These patches are also available via the 'nospec-v4' git branch here: git://git.kernel.org/pub/scm/linux/kernel/git/djbw/linux nospec-v4 Note that the BPF fix for Spectre variant1 is merged for 4.15-rc8. : https://googleprojectzero.blogspot.co.uk/2018/01/reading-privileged-memory-with-side.html --- Dan Williams (9): asm/nospec, array_ptr: sanitize speculative array de-references x86: implement array_ptr_mask() x86: introduce __uaccess_begin_nospec and ifence x86, __get_user: use __uaccess_begin_nospec x86, get_user: use pointer masking to limit speculation x86: narrow out of bounds syscalls to sys_read under speculation vfs, fdtable: prevent bounds-check bypass via speculative execution kvm, x86: fix spectre-v1 mitigation nl80211: sanitize array index in parse_txq_params Mark Rutland (1): Documentation: document array_ptr Documentation/speculation.txt | 143 +++++++++++++++++++++++++++++++++++++ arch/x86/entry/entry_64.S | 2 + arch/x86/include/asm/barrier.h | 28 +++++++ arch/x86/include/asm/msr.h | 3 - arch/x86/include/asm/smap.h | 24 ++++++ arch/x86/include/asm/uaccess.h | 15 +++- arch/x86/include/asm/uaccess_32.h | 6 +- arch/x86/include/asm/uaccess_64.h | 12 ++- arch/x86/kvm/vmx.c | 19 ++--- arch/x86/lib/getuser.S | 5 + arch/x86/lib/usercopy_32.c | 8 +- include/linux/fdtable.h | 7 +- include/linux/nospec.h | 65 +++++++++++++++++ net/wireless/nl80211.c | 10 ++- 14 files changed, 312 insertions(+), 35 deletions(-) create mode 100644 Documentation/speculation.txt create mode 100644 include/linux/nospec.h
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