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>
78 lines
2.3 KiB
C
78 lines
2.3 KiB
C
/*
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* Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE
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* Copyright 2003 Andi Kleen, SuSE Labs.
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*
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* Modified for x86 32 bit architecture by
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* Stefani Seibold <stefani@seibold.net>
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* sponsored by Rohde & Schwarz GmbH & Co. KG Munich/Germany
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*
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* Thanks to hpa@transmeta.com for some useful hint.
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* Special thanks to Ingo Molnar for his early experience with
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* a different vsyscall implementation for Linux/IA32 and for the name.
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*
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*/
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#include <linux/timekeeper_internal.h>
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#include <asm/vgtod.h>
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#include <asm/vvar.h>
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int vclocks_used __read_mostly;
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DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data);
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void update_vsyscall_tz(void)
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{
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vsyscall_gtod_data.tz_minuteswest = sys_tz.tz_minuteswest;
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vsyscall_gtod_data.tz_dsttime = sys_tz.tz_dsttime;
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}
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void update_vsyscall(struct timekeeper *tk)
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{
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int vclock_mode = tk->tkr_mono.clock->archdata.vclock_mode;
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struct vsyscall_gtod_data *vdata = &vsyscall_gtod_data;
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/* Mark the new vclock used. */
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BUILD_BUG_ON(VCLOCK_MAX >= 32);
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WRITE_ONCE(vclocks_used, READ_ONCE(vclocks_used) | (1 << vclock_mode));
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gtod_write_begin(vdata);
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/* copy vsyscall data */
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vdata->vclock_mode = vclock_mode;
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vdata->cycle_last = tk->tkr_mono.cycle_last;
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vdata->mask = tk->tkr_mono.mask;
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vdata->mult = tk->tkr_mono.mult;
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vdata->shift = tk->tkr_mono.shift;
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vdata->wall_time_sec = tk->xtime_sec;
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vdata->wall_time_snsec = tk->tkr_mono.xtime_nsec;
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vdata->monotonic_time_sec = tk->xtime_sec
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+ tk->wall_to_monotonic.tv_sec;
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vdata->monotonic_time_snsec = tk->tkr_mono.xtime_nsec
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+ ((u64)tk->wall_to_monotonic.tv_nsec
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<< tk->tkr_mono.shift);
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while (vdata->monotonic_time_snsec >=
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(((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
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vdata->monotonic_time_snsec -=
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((u64)NSEC_PER_SEC) << tk->tkr_mono.shift;
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vdata->monotonic_time_sec++;
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}
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vdata->wall_time_coarse_sec = tk->xtime_sec;
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vdata->wall_time_coarse_nsec = (long)(tk->tkr_mono.xtime_nsec >>
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tk->tkr_mono.shift);
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vdata->monotonic_time_coarse_sec =
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vdata->wall_time_coarse_sec + tk->wall_to_monotonic.tv_sec;
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vdata->monotonic_time_coarse_nsec =
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vdata->wall_time_coarse_nsec + tk->wall_to_monotonic.tv_nsec;
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while (vdata->monotonic_time_coarse_nsec >= NSEC_PER_SEC) {
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vdata->monotonic_time_coarse_nsec -= NSEC_PER_SEC;
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vdata->monotonic_time_coarse_sec++;
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}
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gtod_write_end(vdata);
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}
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