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[PATCH AUTOSEL 4.4 01/12] Input: elantech - enable middle button support on 2 ThinkPads

by Sasha Levin

From: Aaron Ma <aaron.ma(a)canonical.com> [ Upstream commit aa440de3058a3ef530851f9ef373fbb5f694dbc3 ] Adding 2 new touchpad PNPIDs to enable middle button support. Signed-off-by: Aaron Ma <aaron.ma(a)canonical.com> Signed-off-by: Dmitry Torokhov <dmitry.torokhov(a)gmail.com> Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- drivers/input/mouse/elantech.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c index 4c1e527f14a5..7b942ee364b6 100644 --- a/drivers/input/mouse/elantech.c +++ b/drivers/input/mouse/elantech.c @@ -1191,6 +1191,8 @@ static const char * const middle_button_pnp_ids[] = { "LEN2132", /* ThinkPad P52 */ "LEN2133", /* ThinkPad P72 w/ NFC */ "LEN2134", /* ThinkPad P72 */ + "LEN0407", + "LEN0408", NULL }; -- 2.20.1

6 years

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[PATCH AUTOSEL 4.9 01/21] Input: elantech - enable middle button support on 2 ThinkPads

by Sasha Levin

From: Aaron Ma <aaron.ma(a)canonical.com> [ Upstream commit aa440de3058a3ef530851f9ef373fbb5f694dbc3 ] Adding 2 new touchpad PNPIDs to enable middle button support. Signed-off-by: Aaron Ma <aaron.ma(a)canonical.com> Signed-off-by: Dmitry Torokhov <dmitry.torokhov(a)gmail.com> Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- drivers/input/mouse/elantech.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c index 38edf8f5bf8a..15be3ee6cc50 100644 --- a/drivers/input/mouse/elantech.c +++ b/drivers/input/mouse/elantech.c @@ -1187,6 +1187,8 @@ static const char * const middle_button_pnp_ids[] = { "LEN2132", /* ThinkPad P52 */ "LEN2133", /* ThinkPad P72 w/ NFC */ "LEN2134", /* ThinkPad P72 */ + "LEN0407", + "LEN0408", NULL }; -- 2.20.1

6 years

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[PATCH AUTOSEL 4.14 01/35] Input: elantech - enable middle button support on 2 ThinkPads

by Sasha Levin

From: Aaron Ma <aaron.ma(a)canonical.com> [ Upstream commit aa440de3058a3ef530851f9ef373fbb5f694dbc3 ] Adding 2 new touchpad PNPIDs to enable middle button support. Signed-off-by: Aaron Ma <aaron.ma(a)canonical.com> Signed-off-by: Dmitry Torokhov <dmitry.torokhov(a)gmail.com> Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- drivers/input/mouse/elantech.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c index fda33fc3ffcc..ab4888d043f0 100644 --- a/drivers/input/mouse/elantech.c +++ b/drivers/input/mouse/elantech.c @@ -1191,6 +1191,8 @@ static const char * const middle_button_pnp_ids[] = { "LEN2132", /* ThinkPad P52 */ "LEN2133", /* ThinkPad P72 w/ NFC */ "LEN2134", /* ThinkPad P72 */ + "LEN0407", + "LEN0408", NULL }; -- 2.20.1

6 years

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Linux 4.14.131

by Greg KH

I'm announcing the release of the 4.14.131 kernel. All users of the 4.14 kernel series must upgrade. The updated 4.14.y git tree can be found at: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git linux-4.14.y and can be browsed at the normal kernel.org git web browser: https://git.kernel.org/?p=linux/kernel/git/stable/linux-stable.git;a=summary thanks, greg k-h ------------ Makefile | 2 +- net/ipv4/tcp_output.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) Eric Dumazet (1): tcp: refine memory limit test in tcp_fragment() Greg Kroah-Hartman (1): Linux 4.14.131

6 years

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Linux 4.9.184

by Greg KH

I'm announcing the release of the 4.9.184 kernel. All users of the 4.9 kernel series must upgrade. The updated 4.9.y git tree can be found at: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git linux-4.9.y and can be browsed at the normal kernel.org git web browser: https://git.kernel.org/?p=linux/kernel/git/stable/linux-stable.git;a=summary thanks, greg k-h ------------ Makefile | 2 +- net/ipv4/tcp_output.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) Eric Dumazet (1): tcp: refine memory limit test in tcp_fragment() Greg Kroah-Hartman (1): Linux 4.9.184

6 years

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Linux 4.4.184

by Greg KH

I'm announcing the release of the 4.4.184 kernel. All users of the 4.4 kernel series must upgrade. The updated 4.4.y git tree can be found at: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git linux-4.4.y and can be browsed at the normal kernel.org git web browser: https://git.kernel.org/?p=linux/kernel/git/stable/linux-stable.git;a=summary thanks, greg k-h ------------ Makefile | 2 +- net/ipv4/tcp_output.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) Eric Dumazet (1): tcp: refine memory limit test in tcp_fragment() Greg Kroah-Hartman (1): Linux 4.4.184

6 years

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[PATCH AUTOSEL 5.1 01/95] ARM: dts: dra76x: Disable rtc target module

by Sasha Levin

From: Keerthy <j-keerthy(a)ti.com> [ Upstream commit f7b9cb944a5d41fdede4e928a47e9d5fce5169d7 ] rtc is fused out on dra76 and accessing target module register is causing a boot crash hence disable it. Fixes: 549fce068a3112 ("ARM: dts: dra7: Add l4 interconnect hierarchy and ti-sysc data") Signed-off-by: Keerthy <j-keerthy(a)ti.com> Signed-off-by: Tony Lindgren <tony(a)atomide.com> Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- arch/arm/boot/dts/dra7-l4.dtsi | 2 +- arch/arm/boot/dts/dra76x.dtsi | 4 ++++ 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/arm/boot/dts/dra7-l4.dtsi b/arch/arm/boot/dts/dra7-l4.dtsi index 414f1cd68733..73f5c050f586 100644 --- a/arch/arm/boot/dts/dra7-l4.dtsi +++ b/arch/arm/boot/dts/dra7-l4.dtsi @@ -3543,7 +3543,7 @@ }; }; - target-module@38000 { /* 0x48838000, ap 29 12.0 */ + rtctarget: target-module@38000 { /* 0x48838000, ap 29 12.0 */ compatible = "ti,sysc-omap4-simple", "ti,sysc"; ti,hwmods = "rtcss"; reg = <0x38074 0x4>, diff --git a/arch/arm/boot/dts/dra76x.dtsi b/arch/arm/boot/dts/dra76x.dtsi index 9ee45aa365d8..5c437271d307 100644 --- a/arch/arm/boot/dts/dra76x.dtsi +++ b/arch/arm/boot/dts/dra76x.dtsi @@ -81,3 +81,7 @@ reg = <0x3fc>; }; }; + +&rtctarget { + status = "disabled"; +}; -- 2.20.1

6 years

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Клиентские базы! Email: prodawez@armyspy.com Узнайте подробнее!

by stable＠vger.kernel.org

Клиентские базы! Email: prodawez(a)armyspy.com Узнайте подробнее!

6 years

1
0
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[PATCH] drm/nouveau: Enable i2c pads & busses during preinit

by Lyude Paul

It turns out that while disabling i2c bus access from software when the GPU is suspended was a step in the right direction with: commit 342406e4fbba ("drm/nouveau/i2c: Disable i2c bus access after ->fini()") We also ended up accidentally breaking the vbios init scripts on some older Tesla GPUs, as apparently said scripts can actually use the i2c bus. Since these scripts are executed before initializing any subdevices, we end up failing to acquire access to the i2c bus which has left a number of cards with their fan controllers uninitialized. Luckily this doesn't break hardware - it just means the fan gets stuck at 100%. This also means that we've always been using our i2c busses before initializing them during the init scripts for older GPUs, we just didn't notice it until we started preventing them from being used until init. It's pretty impressive this never caused us any issues before! So, fix this by initializing our i2c pad and busses during subdev pre-init. We skip initializing aux busses during pre-init, as those are guaranteed to only ever be used by nouveau for DP aux transactions. Signed-off-by: Lyude Paul <lyude(a)redhat.com> Tested-by: Marc Meledandri <m.meledandri(a)gmail.com> Fixes: 342406e4fbba ("drm/nouveau/i2c: Disable i2c bus access after ->fini()") Cc: stable(a)vger.kernel.org --- .../gpu/drm/nouveau/nvkm/subdev/i2c/base.c | 20 +++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/i2c/base.c b/drivers/gpu/drm/nouveau/nvkm/subdev/i2c/base.c index ecacb22834d7..719345074711 100644 --- a/drivers/gpu/drm/nouveau/nvkm/subdev/i2c/base.c +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/i2c/base.c @@ -184,6 +184,25 @@ nvkm_i2c_fini(struct nvkm_subdev *subdev, bool suspend) return 0; } +static int +nvkm_i2c_preinit(struct nvkm_subdev *subdev) +{ + struct nvkm_i2c *i2c = nvkm_i2c(subdev); + struct nvkm_i2c_bus *bus; + struct nvkm_i2c_pad *pad; + + /* + * We init our i2c busses as early as possible, since they may be + * needed by the vbios init scripts on some cards + */ + list_for_each_entry(pad, &i2c->pad, head) + nvkm_i2c_pad_init(pad); + list_for_each_entry(bus, &i2c->bus, head) + nvkm_i2c_bus_init(bus); + + return 0; +} + static int nvkm_i2c_init(struct nvkm_subdev *subdev) { @@ -238,6 +257,7 @@ nvkm_i2c_dtor(struct nvkm_subdev *subdev) static const struct nvkm_subdev_func nvkm_i2c = { .dtor = nvkm_i2c_dtor, + .preinit = nvkm_i2c_preinit, .init = nvkm_i2c_init, .fini = nvkm_i2c_fini, .intr = nvkm_i2c_intr, -- 2.21.0

6 years

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[PATCH v6] Documentation: Add section about CPU vulnerabilities for Spectre

by Tim Chen

Add documentation for Spectre vulnerability and the mitigation mechanisms: - Explain the problem and risks - Document the mitigation mechanisms - Document the command line controls - Document the sysfs files Co-developed-by: Andi Kleen <ak(a)linux.intel.com> Signed-off-by: Andi Kleen <ak(a)linux.intel.com> Co-developed-by: Tim Chen <tim.c.chen(a)linux.intel.com> Signed-off-by: Tim Chen <tim.c.chen(a)linux.intel.com> Reviewed-by: Thomas Gleixner <tglx(a)linutronix.de> Cc: stable(a)vger.kernel.org --- Documentation/admin-guide/hw-vuln/index.rst | 1 + Documentation/admin-guide/hw-vuln/spectre.rst | 697 ++++++++++++++++++ Documentation/userspace-api/spec_ctrl.rst | 2 + 3 files changed, 700 insertions(+) create mode 100644 Documentation/admin-guide/hw-vuln/spectre.rst diff --git a/Documentation/admin-guide/hw-vuln/index.rst b/Documentation/admin-guide/hw-vuln/index.rst index ffc064c1ec68..49311f3da6f2 100644 --- a/Documentation/admin-guide/hw-vuln/index.rst +++ b/Documentation/admin-guide/hw-vuln/index.rst @@ -9,5 +9,6 @@ are configurable at compile, boot or run time. .. toctree:: :maxdepth: 1 + spectre l1tf mds diff --git a/Documentation/admin-guide/hw-vuln/spectre.rst b/Documentation/admin-guide/hw-vuln/spectre.rst new file mode 100644 index 000000000000..25f3b2532198 --- /dev/null +++ b/Documentation/admin-guide/hw-vuln/spectre.rst @@ -0,0 +1,697 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Spectre Side Channels +===================== + +Spectre is a class of side channel attacks that exploit branch prediction +and speculative execution on modern CPUs to read memory, possibly +bypassing access controls. Speculative execution side channel exploits +do not modify memory but attempt to infer privileged data in the memory. + +This document covers Spectre variant 1 and Spectre variant 2. + +Affected processors +------------------- + +Speculative execution side channel methods affect a wide range of modern +high performance processors, since most modern high speed processors +use branch prediction and speculative execution. + +The following CPUs are vulnerable: + + - Intel Core, Atom, Pentium, and Xeon processors + + - AMD Phenom, EPYC, and Zen processors + + - IBM POWER and zSeries processors + + - Higher end ARM processors + + - Apple CPUs + + - Higher end MIPS CPUs + + - Likely most other high performance CPUs. Contact your CPU vendor for details. + +Whether a processor is affected or not can be read out from the Spectre +vulnerability files in sysfs. See :ref:`spectre_sys_info`. + +Related CVEs +------------ + +The following CVE entries describe Spectre variants: + + ============= ======================= ================= + CVE-2017-5753 Bounds check bypass Spectre variant 1 + CVE-2017-5715 Branch target injection Spectre variant 2 + ============= ======================= ================= + +Problem +------- + +CPUs use speculative operations to improve performance. That may leave +traces of memory accesses or computations in the processor's caches, +buffers, and branch predictors. Malicious software may be able to +influence the speculative execution paths, and then use the side effects +of the speculative execution in the CPUs' caches and buffers to infer +privileged data touched during the speculative execution. + +Spectre variant 1 attacks take advantage of speculative execution of +conditional branches, while Spectre variant 2 attacks use speculative +execution of indirect branches to leak privileged memory. +See :ref:`[1] <spec_ref1>` :ref:`[5] <spec_ref5>` :ref:`[7] <spec_ref7>` +:ref:`[10] <spec_ref10>` :ref:`[11] <spec_ref11>`. + +Spectre variant 1 (Bounds Check Bypass) +--------------------------------------- + +The bounds check bypass attack :ref:`[2] <spec_ref2>` takes advantage +of speculative execution that bypasses conditional branch instructions +used for memory access bounds check (e.g. checking if the index of an +array results in memory access within a valid range). This results in +memory accesses to invalid memory (with out-of-bound index) that are +done speculatively before validation checks resolve. Such speculative +memory accesses can leave side effects, creating side channels which +leak information to the attacker. + +There are some extensions of Spectre variant 1 attacks for reading data +over the network, see :ref:`[12] <spec_ref12>`. However such attacks +are difficult, low bandwidth, fragile, and are considered low risk. + +Spectre variant 2 (Branch Target Injection) +------------------------------------------- + +The branch target injection attack takes advantage of speculative +execution of indirect branches :ref:`[3] <spec_ref3>`. The indirect +branch predictors inside the processor used to guess the target of +indirect branches can be influenced by an attacker, causing gadget code +to be speculatively executed, thus exposing sensitive data touched by +the victim. The side effects left in the CPU's caches during speculative +execution can be measured to infer data values. + +.. _poison_btb: + +In Spectre variant 2 attacks, the attacker can steer speculative indirect +branches in the victim to gadget code by poisoning the branch target +buffer of a CPU used for predicting indirect branch addresses. Such +poisoning could be done by indirect branching into existing code, +with the address offset of the indirect branch under the attacker's +control. Since the branch prediction on impacted hardware does not +fully disambiguate branch address and uses the offset for prediction, +this could cause privileged code's indirect branch to jump to a gadget +code with the same offset. + +The most useful gadgets take an attacker-controlled input parameter (such +as a register value) so that the memory read can be controlled. Gadgets +without input parameters might be possible, but the attacker would have +very little control over what memory can be read, reducing the risk of +the attack revealing useful data. + +One other variant 2 attack vector is for the attacker to poison the +return stack buffer (RSB) :ref:`[13] <spec_ref13>` to cause speculative +subroutine return instruction execution to go to a gadget. An attacker's +imbalanced subroutine call instructions might "poison" entries in the +return stack buffer which are later consumed by a victim's subroutine +return instructions. This attack can be mitigated by flushing the return +stack buffer on context switch, or virtual machine (VM) exit. + +On systems with simultaneous multi-threading (SMT), attacks are possible +from the sibling thread, as level 1 cache and branch target buffer +(BTB) may be shared between hardware threads in a CPU core. A malicious +program running on the sibling thread may influence its peer's BTB to +steer its indirect branch speculations to gadget code, and measure the +speculative execution's side effects left in level 1 cache to infer the +victim's data. + +Attack scenarios +---------------- + +The following list of attack scenarios have been anticipated, but may +not cover all possible attack vectors. + +1. A user process attacking the kernel +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + The attacker passes a parameter to the kernel via a register or + via a known address in memory during a syscall. Such parameter may + be used later by the kernel as an index to an array or to derive + a pointer for a Spectre variant 1 attack. The index or pointer + is invalid, but bound checks are bypassed in the code branch taken + for speculative execution. This could cause privileged memory to be + accessed and leaked. + + For kernel code that has been identified where data pointers could + potentially be influenced for Spectre attacks, new "nospec" accessor + macros are used to prevent speculative loading of data. + + Spectre variant 2 attacker can :ref:`poison <poison_btb>` the branch + target buffer (BTB) before issuing syscall to launch an attack. + After entering the kernel, the kernel could use the poisoned branch + target buffer on indirect jump and jump to gadget code in speculative + execution. + + If an attacker tries to control the memory addresses leaked during + speculative execution, he would also need to pass a parameter to the + gadget, either through a register or a known address in memory. After + the gadget has executed, he can measure the side effect. + + The kernel can protect itself against consuming poisoned branch + target buffer entries by using return trampolines (also known as + "retpoline") :ref:`[3] <spec_ref3>` :ref:`[9] <spec_ref9>` for all + indirect branches. Return trampolines trap speculative execution paths + to prevent jumping to gadget code during speculative execution. + x86 CPUs with Enhanced Indirect Branch Restricted Speculation + (Enhanced IBRS) available in hardware should use the feature to + mitigate Spectre variant 2 instead of retpoline. Enhanced IBRS is + more efficient than retpoline. + + There may be gadget code in firmware which could be exploited with + Spectre variant 2 attack by a rogue user process. To mitigate such + attacks on x86, Indirect Branch Restricted Speculation (IBRS) feature + is turned on before the kernel invokes any firmware code. + +2. A user process attacking another user process +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + A malicious user process can try to attack another user process, + either via a context switch on the same hardware thread, or from the + sibling hyperthread sharing a physical processor core on simultaneous + multi-threading (SMT) system. + + Spectre variant 1 attacks generally require passing parameters + between the processes, which needs a data passing relationship, such + as remote procedure calls (RPC). Those parameters are used in gadget + code to derive invalid data pointers accessing privileged memory in + the attacked process. + + Spectre variant 2 attacks can be launched from a rogue process by + :ref:`poisoning <poison_btb>` the branch target buffer. This can + influence the indirect branch targets for a victim process that either + runs later on the same hardware thread, or running concurrently on + a sibling hardware thread sharing the same physical core. + + A user process can protect itself against Spectre variant 2 attacks + by using the prctl() syscall to disable indirect branch speculation + for itself. An administrator can also cordon off an unsafe process + from polluting the branch target buffer by disabling the process's + indirect branch speculation. This comes with a performance cost + from not using indirect branch speculation and clearing the branch + target buffer. When SMT is enabled on x86, for a process that has + indirect branch speculation disabled, Single Threaded Indirect Branch + Predictors (STIBP) :ref:`[4] <spec_ref4>` are turned on to prevent the + sibling thread from controlling branch target buffer. In addition, + the Indirect Branch Prediction Barrier (IBPB) is issued to clear the + branch target buffer when context switching to and from such process. + + On x86, the return stack buffer is stuffed on context switch. + This prevents the branch target buffer from being used for branch + prediction when the return stack buffer underflows while switching to + a deeper call stack. Any poisoned entries in the return stack buffer + left by the previous process will also be cleared. + + User programs should use address space randomization to make attacks + more difficult (Set /proc/sys/kernel/randomize_va_space = 1 or 2). + +3. A virtualized guest attacking the host +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + The attack mechanism is similar to how user processes attack the + kernel. The kernel is entered via hyper-calls or other virtualization + exit paths. + + For Spectre variant 1 attacks, rogue guests can pass parameters + (e.g. in registers) via hyper-calls to derive invalid pointers to + speculate into privileged memory after entering the kernel. For places + where such kernel code has been identified, nospec accessor macros + are used to stop speculative memory access. + + For Spectre variant 2 attacks, rogue guests can :ref:`poison + <poison_btb>` the branch target buffer or return stack buffer, causing + the kernel to jump to gadget code in the speculative execution paths. + + To mitigate variant 2, the host kernel can use return trampolines + for indirect branches to bypass the poisoned branch target buffer, + and flushing the return stack buffer on VM exit. This prevents rogue + guests from affecting indirect branching in the host kernel. + + To protect host processes from rogue guests, host processes can have + indirect branch speculation disabled via prctl(). The branch target + buffer is cleared before context switching to such processes. + +4. A virtualized guest attacking other guest +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + A rogue guest may attack another guest to get data accessible by the + other guest. + + Spectre variant 1 attacks are possible if parameters can be passed + between guests. This may be done via mechanisms such as shared memory + or message passing. Such parameters could be used to derive data + pointers to privileged data in guest. The privileged data could be + accessed by gadget code in the victim's speculation paths. + + Spectre variant 2 attacks can be launched from a rogue guest by + :ref:`poisoning <poison_btb>` the branch target buffer or the return + stack buffer. Such poisoned entries could be used to influence + speculation execution paths in the victim guest. + + Linux kernel mitigates attacks to other guests running in the same + CPU hardware thread by flushing the return stack buffer on VM exit, + and clearing the branch target buffer before switching to a new guest. + + If SMT is used, Spectre variant 2 attacks from an untrusted guest + in the sibling hyperthread can be mitigated by the administrator, + by turning off the unsafe guest's indirect branch speculation via + prctl(). A guest can also protect itself by turning on microcode + based mitigations (such as IBPB or STIBP on x86) within the guest. + +.. _spectre_sys_info: + +Spectre system information +-------------------------- + +The Linux kernel provides a sysfs interface to enumerate the current +mitigation status of the system for Spectre: whether the system is +vulnerable, and which mitigations are active. + +The sysfs file showing Spectre variant 1 mitigation status is: + + /sys/devices/system/cpu/vulnerabilities/spectre_v1 + +The possible values in this file are: + + ======================================= ================================= + 'Mitigation: __user pointer sanitation' Protection in kernel on a case by + case base with explicit pointer + sanitation. + ======================================= ================================= + +However, the protections are put in place on a case by case basis, +and there is no guarantee that all possible attack vectors for Spectre +variant 1 are covered. + +The spectre_v2 kernel file reports if the kernel has been compiled with +retpoline mitigation or if the CPU has hardware mitigation, and if the +CPU has support for additional process-specific mitigation. + +This file also reports CPU features enabled by microcode to mitigate +attack between user processes: + +1. Indirect Branch Prediction Barrier (IBPB) to add additional + isolation between processes of different users. +2. Single Thread Indirect Branch Predictors (STIBP) to add additional + isolation between CPU threads running on the same core. + +These CPU features may impact performance when used and can be enabled +per process on a case-by-case base. + +The sysfs file showing Spectre variant 2 mitigation status is: + + /sys/devices/system/cpu/vulnerabilities/spectre_v2 + +The possible values in this file are: + + - Kernel status: + + ==================================== ================================= + 'Not affected' The processor is not vulnerable + 'Vulnerable' Vulnerable, no mitigation + 'Mitigation: Full generic retpoline' Software-focused mitigation + 'Mitigation: Full AMD retpoline' AMD-specific software mitigation + 'Mitigation: Enhanced IBRS' Hardware-focused mitigation + ==================================== ================================= + + - Firmware status: Show if Indirect Branch Restricted Speculation (IBRS) is + used to protect against Spectre variant 2 attacks when calling firmware (x86 only). + + ========== ============================================================= + 'IBRS_FW' Protection against user program attacks when calling firmware + ========== ============================================================= + + - Indirect branch prediction barrier (IBPB) status for protection between + processes of different users. This feature can be controlled through + prctl() per process, or through kernel command line options. This is + an x86 only feature. For more details see below. + + =================== ======================================================== + 'IBPB: disabled' IBPB unused + 'IBPB: always-on' Use IBPB on all tasks + 'IBPB: conditional' Use IBPB on SECCOMP or indirect branch restricted tasks + =================== ======================================================== + + - Single threaded indirect branch prediction (STIBP) status for protection + between different hyper threads. This feature can be controlled through + prctl per process, or through kernel command line options. This is x86 + only feature. For more details see below. + + ==================== ======================================================== + 'STIBP: disabled' STIBP unused + 'STIBP: forced' Use STIBP on all tasks + 'STIBP: conditional' Use STIBP on SECCOMP or indirect branch restricted tasks + ==================== ======================================================== + + - Return stack buffer (RSB) protection status: + + ============= =========================================== + 'RSB filling' Protection of RSB on context switch enabled + ============= =========================================== + +Full mitigation might require a microcode update from the CPU +vendor. When the necessary microcode is not available, the kernel will +report vulnerability. + +Turning on mitigation for Spectre variant 1 and Spectre variant 2 +----------------------------------------------------------------- + +1. Kernel mitigation +^^^^^^^^^^^^^^^^^^^^ + + For the Spectre variant 1, vulnerable kernel code (as determined + by code audit or scanning tools) is annotated on a case by case + basis to use nospec accessor macros for bounds clipping :ref:`[2] + <spec_ref2>` to avoid any usable disclosure gadgets. However, it may + not cover all attack vectors for Spectre variant 1. + + For Spectre variant 2 mitigation, the compiler turns indirect calls or + jumps in the kernel into equivalent return trampolines (retpolines) + :ref:`[3] <spec_ref3>` :ref:`[9] <spec_ref9>` to go to the target + addresses. Speculative execution paths under retpolines are trapped + in an infinite loop to prevent any speculative execution jumping to + a gadget. + + To turn on retpoline mitigation on a vulnerable CPU, the kernel + needs to be compiled with a gcc compiler that supports the + -mindirect-branch=thunk-extern -mindirect-branch-register options. + If the kernel is compiled with a Clang compiler, the compiler needs + to support -mretpoline-external-thunk option. The kernel config + CONFIG_RETPOLINE needs to be turned on, and the CPU needs to run with + the latest updated microcode. + + On Intel Skylake-era systems the mitigation covers most, but not all, + cases. See :ref:`[3] <spec_ref3>` for more details. + + On CPUs with hardware mitigation for Spectre variant 2 (e.g. Enhanced + IBRS on x86), retpoline is automatically disabled at run time. + + The retpoline mitigation is turned on by default on vulnerable + CPUs. It can be forced on or off by the administrator + via the kernel command line and sysfs control files. See + :ref:`spectre_mitigation_control_command_line`. + + On x86, indirect branch restricted speculation is turned on by default + before invoking any firmware code to prevent Spectre variant 2 exploits + using the firmware. + + Using kernel address space randomization (CONFIG_RANDOMIZE_SLAB=y + and CONFIG_SLAB_FREELIST_RANDOM=y in the kernel configuration) makes + attacks on the kernel generally more difficult. + +2. User program mitigation +^^^^^^^^^^^^^^^^^^^^^^^^^^ + + User programs can mitigate Spectre variant 1 using LFENCE or "bounds + clipping". For more details see :ref:`[2] <spec_ref2>`. + + For Spectre variant 2 mitigation, individual user programs + can be compiled with return trampolines for indirect branches. + This protects them from consuming poisoned entries in the branch + target buffer left by malicious software. Alternatively, the + programs can disable their indirect branch speculation via prctl() + (See :ref:`Documentation/userspace-api/spec_ctrl.rst <set_spec_ctrl>`). + On x86, this will turn on STIBP to guard against attacks from the + sibling thread when the user program is running, and use IBPB to + flush the branch target buffer when switching to/from the program. + + Restricting indirect branch speculation on a user program will + also prevent the program from launching a variant 2 attack + on x86. All sand-boxed SECCOMP programs have indirect branch + speculation restricted by default. Administrators can change + that behavior via the kernel command line and sysfs control files. + See :ref:`spectre_mitigation_control_command_line`. + + Programs that disable their indirect branch speculation will have + more overhead and run slower. + + User programs should use address space randomization + (/proc/sys/kernel/randomize_va_space = 1 or 2) to make attacks more + difficult. + +3. VM mitigation +^^^^^^^^^^^^^^^^ + + Within the kernel, Spectre variant 1 attacks from rogue guests are + mitigated on a case by case basis in VM exit paths. Vulnerable code + uses nospec accessor macros for "bounds clipping", to avoid any + usable disclosure gadgets. However, this may not cover all variant + 1 attack vectors. + + For Spectre variant 2 attacks from rogue guests to the kernel, the + Linux kernel uses retpoline or Enhanced IBRS to prevent consumption of + poisoned entries in branch target buffer left by rogue guests. It also + flushes the return stack buffer on every VM exit to prevent a return + stack buffer underflow so poisoned branch target buffer could be used, + or attacker guests leaving poisoned entries in the return stack buffer. + + To mitigate guest-to-guest attacks in the same CPU hardware thread, + the branch target buffer is sanitized by flushing before switching + to a new guest on a CPU. + + The above mitigations are turned on by default on vulnerable CPUs. + + To mitigate guest-to-guest attacks from sibling thread when SMT is + in use, an untrusted guest running in the sibling thread can have + its indirect branch speculation disabled by administrator via prctl(). + + The kernel also allows guests to use any microcode based mitigation + they choose to use (such as IBPB or STIBP on x86) to protect themselves. + +.. _spectre_mitigation_control_command_line: + +Mitigation control on the kernel command line +--------------------------------------------- + +Spectre variant 2 mitigation can be disabled or force enabled at the +kernel command line. + + nospectre_v2 + + [X86] Disable all mitigations for the Spectre variant 2 + (indirect branch prediction) vulnerability. System may + allow data leaks with this option, which is equivalent + to spectre_v2=off. + + + spectre_v2= + + [X86] Control mitigation of Spectre variant 2 + (indirect branch speculation) vulnerability. + The default operation protects the kernel from + user space attacks. + + on + unconditionally enable, implies + spectre_v2_user=on + off + unconditionally disable, implies + spectre_v2_user=off + auto + kernel detects whether your CPU model is + vulnerable + + Selecting 'on' will, and 'auto' may, choose a + mitigation method at run time according to the + CPU, the available microcode, the setting of the + CONFIG_RETPOLINE configuration option, and the + compiler with which the kernel was built. + + Selecting 'on' will also enable the mitigation + against user space to user space task attacks. + + Selecting 'off' will disable both the kernel and + the user space protections. + + Specific mitigations can also be selected manually: + + retpoline + replace indirect branches + retpoline,generic + google's original retpoline + retpoline,amd + AMD-specific minimal thunk + + Not specifying this option is equivalent to + spectre_v2=auto. + +For user space mitigation: + + spectre_v2_user= + + [X86] Control mitigation of Spectre variant 2 + (indirect branch speculation) vulnerability between + user space tasks + + on + Unconditionally enable mitigations. Is + enforced by spectre_v2=on + + off + Unconditionally disable mitigations. Is + enforced by spectre_v2=off + + prctl + Indirect branch speculation is enabled, + but mitigation can be enabled via prctl + per thread. The mitigation control state + is inherited on fork. + + prctl,ibpb + Like "prctl" above, but only STIBP is + controlled per thread. IBPB is issued + always when switching between different user + space processes. + + seccomp + Same as "prctl" above, but all seccomp + threads will enable the mitigation unless + they explicitly opt out. + + seccomp,ibpb + Like "seccomp" above, but only STIBP is + controlled per thread. IBPB is issued + always when switching between different + user space processes. + + auto + Kernel selects the mitigation depending on + the available CPU features and vulnerability. + + Default mitigation: + If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl" + + Not specifying this option is equivalent to + spectre_v2_user=auto. + + In general the kernel by default selects + reasonable mitigations for the current CPU. To + disable Spectre variant 2 mitigations, boot with + spectre_v2=off. Spectre variant 1 mitigations + cannot be disabled. + +Mitigation selection guide +-------------------------- + +1. Trusted userspace +^^^^^^^^^^^^^^^^^^^^ + + If all userspace applications are from trusted sources and do not + execute externally supplied untrusted code, then the mitigations can + be disabled. + +2. Protect sensitive programs +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + For security-sensitive programs that have secrets (e.g. crypto + keys), protection against Spectre variant 2 can be put in place by + disabling indirect branch speculation when the program is running + (See :ref:`Documentation/userspace-api/spec_ctrl.rst <set_spec_ctrl>`). + +3. Sandbox untrusted programs +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + Untrusted programs that could be a source of attacks can be cordoned + off by disabling their indirect branch speculation when they are run + (See :ref:`Documentation/userspace-api/spec_ctrl.rst <set_spec_ctrl>`). + This prevents untrusted programs from polluting the branch target + buffer. All programs running in SECCOMP sandboxes have indirect + branch speculation restricted by default. This behavior can be + changed via the kernel command line and sysfs control files. See + :ref:`spectre_mitigation_control_command_line`. + +3. High security mode +^^^^^^^^^^^^^^^^^^^^^ + + All Spectre variant 2 mitigations can be forced on + at boot time for all programs (See the "on" option in + :ref:`spectre_mitigation_control_command_line`). This will add + overhead as indirect branch speculations for all programs will be + restricted. + + On x86, branch target buffer will be flushed with IBPB when switching + to a new program. STIBP is left on all the time to protect programs + against variant 2 attacks originating from programs running on + sibling threads. + + Alternatively, STIBP can be used only when running programs + whose indirect branch speculation is explicitly disabled, + while IBPB is still used all the time when switching to a new + program to clear the branch target buffer (See "ibpb" option in + :ref:`spectre_mitigation_control_command_line`). This "ibpb" option + has less performance cost than the "on" option, which leaves STIBP + on all the time. + +References on Spectre +--------------------- + +Intel white papers: + +.. _spec_ref1: + +[1] `Intel analysis of speculative execution side channels <https://newsroom.intel.com/wp-content/uploads/sites/11/2018/01/Intel-Analys…>`_. + +.. _spec_ref2: + +[2] `Bounds check bypass <https://software.intel.com/security-software-guidance/software-guidance/bou…>`_. + +.. _spec_ref3: + +[3] `Deep dive: Retpoline: A branch target injection mitigation <https://software.intel.com/security-software-guidance/insights/deep-dive-re…>`_. + +.. _spec_ref4: + +[4] `Deep Dive: Single Thread Indirect Branch Predictors <https://software.intel.com/security-software-guidance/insights/deep-dive-si…>`_. + +AMD white papers: + +.. _spec_ref5: + +[5] `AMD64 technology indirect branch control extension <https://developer.amd.com/wp-content/resources/Architecture_Guidelines_Upda…>`_. + +.. _spec_ref6: + +[6] `Software techniques for managing speculation on AMD processors <https://developer.amd.com/wp-content/resources/90343-B_SoftwareTechniquesfo…>`_. + +ARM white papers: + +.. _spec_ref7: + +[7] `Cache speculation side-channels <https://developer.arm.com/support/arm-security-updates/speculative-processo…>`_. + +.. _spec_ref8: + +[8] `Cache speculation issues update <https://developer.arm.com/support/arm-security-updates/speculative-processo…>`_. + +Google white paper: + +.. _spec_ref9: + +[9] `Retpoline: a software construct for preventing branch-target-injection <https://support.google.com/faqs/answer/7625886>`_. + +MIPS white paper: + +.. _spec_ref10: + +[10] `MIPS: response on speculative execution and side channel vulnerabilities <https://www.mips.com/blog/mips-response-on-speculative-execution-and-side-c…>`_. + +Academic papers: + +.. _spec_ref11: + +[11] `Spectre Attacks: Exploiting Speculative Execution <https://spectreattack.com/spectre.pdf>`_. + +.. _spec_ref12: + +[12] `NetSpectre: Read Arbitrary Memory over Network <https://arxiv.org/abs/1807.10535>`_. + +.. _spec_ref13: + +[13] `Spectre Returns! Speculation Attacks using the Return Stack Buffer <https://www.usenix.org/system/files/conference/woot18/woot18-paper-koruyeh.…>`_. diff --git a/Documentation/userspace-api/spec_ctrl.rst b/Documentation/userspace-api/spec_ctrl.rst index 1129c7550a48..7ddd8f667459 100644 --- a/Documentation/userspace-api/spec_ctrl.rst +++ b/Documentation/userspace-api/spec_ctrl.rst @@ -49,6 +49,8 @@ If PR_SPEC_PRCTL is set, then the per-task control of the mitigation is available. If not set, prctl(PR_SET_SPECULATION_CTRL) for the speculation misfeature will fail. +.. _set_spec_ctrl: + PR_SET_SPECULATION_CTRL ----------------------- -- 2.20.1

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