forked from Minki/linux
bd902c5362
It makes me uncomfortable that even modern systems grant every process direct read access to the HPET. While fixing this for real without regressing anything is a mess (unmapping the HPET is tricky because we don't adequately track all the mappings), we can do almost as well by tracking which vclocks have ever been used and only allowing pages associated with used vclocks to be faulted in. This will cause rogue programs that try to peek at the HPET to get SIGBUS instead on most systems. We can't restrict faults to vclock pages that are associated with the currently selected vclock due to a race: a process could start to access the HPET for the first time and race against a switch away from the HPET as the current clocksource. We can't segfault the process trying to peek at the HPET in this case, even though the process isn't going to do anything useful with the data. Signed-off-by: Andy Lutomirski <luto@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/e79d06295625c02512277737ab55085a498ac5d8.1451446564.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
17 lines
444 B
C
17 lines
444 B
C
/* x86-specific clocksource additions */
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#ifndef _ASM_X86_CLOCKSOURCE_H
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#define _ASM_X86_CLOCKSOURCE_H
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#define VCLOCK_NONE 0 /* No vDSO clock available. */
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#define VCLOCK_TSC 1 /* vDSO should use vread_tsc. */
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#define VCLOCK_HPET 2 /* vDSO should use vread_hpet. */
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#define VCLOCK_PVCLOCK 3 /* vDSO should use vread_pvclock. */
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#define VCLOCK_MAX 3
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struct arch_clocksource_data {
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int vclock_mode;
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};
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#endif /* _ASM_X86_CLOCKSOURCE_H */
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