Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86/pti update from Thomas Gleixner:
"Just a single change from the anti-performance departement:
- Add a new PR_SPEC_DISABLE_NOEXEC option which allows to apply the
speculation protections on a process without inheriting the state
on exec.
This remedies a situation where a Java-launcher has speculation
protections enabled because that's the default for JVMs which
causes the launched regular harmless processes to inherit the
protection state which results in unintended performance
degradation"
* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/speculation: Add PR_SPEC_DISABLE_NOEXEC
This commit is contained in:
Linus Torvalds
commit
edaed168e1
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@ -28,18 +28,20 @@ PR_GET_SPECULATION_CTRL returns the state of the speculation misfeature
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which is selected with arg2 of prctl(2). The return value uses bits 0-3 with
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the following meaning:
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==== ===================== ===================================================
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Bit Define Description
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==== ===================== ===================================================
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0 PR_SPEC_PRCTL Mitigation can be controlled per task by
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PR_SET_SPECULATION_CTRL.
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1 PR_SPEC_ENABLE The speculation feature is enabled, mitigation is
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disabled.
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2 PR_SPEC_DISABLE The speculation feature is disabled, mitigation is
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enabled.
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3 PR_SPEC_FORCE_DISABLE Same as PR_SPEC_DISABLE, but cannot be undone. A
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subsequent prctl(..., PR_SPEC_ENABLE) will fail.
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==== ===================== ===================================================
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==== ====================== ==================================================
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Bit Define Description
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==== ====================== ==================================================
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0 PR_SPEC_PRCTL Mitigation can be controlled per task by
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PR_SET_SPECULATION_CTRL.
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1 PR_SPEC_ENABLE The speculation feature is enabled, mitigation is
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disabled.
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2 PR_SPEC_DISABLE The speculation feature is disabled, mitigation is
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enabled.
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3 PR_SPEC_FORCE_DISABLE Same as PR_SPEC_DISABLE, but cannot be undone. A
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subsequent prctl(..., PR_SPEC_ENABLE) will fail.
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4 PR_SPEC_DISABLE_NOEXEC Same as PR_SPEC_DISABLE, but the state will be
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cleared on :manpage:`execve(2)`.
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==== ====================== ==================================================
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If all bits are 0 the CPU is not affected by the speculation misfeature.
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@ -92,6 +94,7 @@ Speculation misfeature controls
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* prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_ENABLE, 0, 0);
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* prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_DISABLE, 0, 0);
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* prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_FORCE_DISABLE, 0, 0);
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* prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_DISABLE_NOEXEC, 0, 0);
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- PR_SPEC_INDIR_BRANCH: Indirect Branch Speculation in User Processes
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(Mitigate Spectre V2 style attacks against user processes)
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@ -798,15 +798,25 @@ static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl)
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if (task_spec_ssb_force_disable(task))
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return -EPERM;
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task_clear_spec_ssb_disable(task);
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task_clear_spec_ssb_noexec(task);
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task_update_spec_tif(task);
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break;
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case PR_SPEC_DISABLE:
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task_set_spec_ssb_disable(task);
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task_clear_spec_ssb_noexec(task);
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task_update_spec_tif(task);
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break;
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case PR_SPEC_FORCE_DISABLE:
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task_set_spec_ssb_disable(task);
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task_set_spec_ssb_force_disable(task);
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task_clear_spec_ssb_noexec(task);
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task_update_spec_tif(task);
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break;
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case PR_SPEC_DISABLE_NOEXEC:
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if (task_spec_ssb_force_disable(task))
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return -EPERM;
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task_set_spec_ssb_disable(task);
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task_set_spec_ssb_noexec(task);
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task_update_spec_tif(task);
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break;
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default:
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@ -885,6 +895,8 @@ static int ssb_prctl_get(struct task_struct *task)
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case SPEC_STORE_BYPASS_PRCTL:
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if (task_spec_ssb_force_disable(task))
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return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
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if (task_spec_ssb_noexec(task))
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return PR_SPEC_PRCTL | PR_SPEC_DISABLE_NOEXEC;
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if (task_spec_ssb_disable(task))
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return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
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return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
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@ -255,6 +255,18 @@ void arch_setup_new_exec(void)
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/* If cpuid was previously disabled for this task, re-enable it. */
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if (test_thread_flag(TIF_NOCPUID))
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enable_cpuid();
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/*
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* Don't inherit TIF_SSBD across exec boundary when
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* PR_SPEC_DISABLE_NOEXEC is used.
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*/
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if (test_thread_flag(TIF_SSBD) &&
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task_spec_ssb_noexec(current)) {
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clear_thread_flag(TIF_SSBD);
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task_clear_spec_ssb_disable(current);
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task_clear_spec_ssb_noexec(current);
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speculation_ctrl_update(task_thread_info(current)->flags);
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}
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}
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static inline void switch_to_bitmap(struct thread_struct *prev,
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@ -1453,6 +1453,7 @@ static inline bool is_percpu_thread(void)
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#define PFA_SPEC_SSB_FORCE_DISABLE 4 /* Speculative Store Bypass force disabled*/
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#define PFA_SPEC_IB_DISABLE 5 /* Indirect branch speculation restricted */
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#define PFA_SPEC_IB_FORCE_DISABLE 6 /* Indirect branch speculation permanently restricted */
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#define PFA_SPEC_SSB_NOEXEC 7 /* Speculative Store Bypass clear on execve() */
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#define TASK_PFA_TEST(name, func) \
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static inline bool task_##func(struct task_struct *p) \
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@ -1481,6 +1482,10 @@ TASK_PFA_TEST(SPEC_SSB_DISABLE, spec_ssb_disable)
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TASK_PFA_SET(SPEC_SSB_DISABLE, spec_ssb_disable)
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TASK_PFA_CLEAR(SPEC_SSB_DISABLE, spec_ssb_disable)
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TASK_PFA_TEST(SPEC_SSB_NOEXEC, spec_ssb_noexec)
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TASK_PFA_SET(SPEC_SSB_NOEXEC, spec_ssb_noexec)
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TASK_PFA_CLEAR(SPEC_SSB_NOEXEC, spec_ssb_noexec)
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TASK_PFA_TEST(SPEC_SSB_FORCE_DISABLE, spec_ssb_force_disable)
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TASK_PFA_SET(SPEC_SSB_FORCE_DISABLE, spec_ssb_force_disable)
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@ -219,6 +219,7 @@ struct prctl_mm_map {
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# define PR_SPEC_ENABLE (1UL << 1)
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# define PR_SPEC_DISABLE (1UL << 2)
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# define PR_SPEC_FORCE_DISABLE (1UL << 3)
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# define PR_SPEC_DISABLE_NOEXEC (1UL << 4)
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/* Reset arm64 pointer authentication keys */
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#define PR_PAC_RESET_KEYS 54
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@ -219,6 +219,7 @@ struct prctl_mm_map {
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# define PR_SPEC_ENABLE (1UL << 1)
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# define PR_SPEC_DISABLE (1UL << 2)
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# define PR_SPEC_FORCE_DISABLE (1UL << 3)
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# define PR_SPEC_DISABLE_NOEXEC (1UL << 4)
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/* Reset arm64 pointer authentication keys */
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#define PR_PAC_RESET_KEYS 54
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