diff options
| author |   Will Deacon <will@kernel.org> | 2021-06-08 19:02:57 +0100 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2021-06-11 13:25:41 +0100 |
| commit | 873c3e89777c8c56f936ae7aceca1a102aac6b9e (patch) | |
| tree | c84816eb04b65c9c89fe29e873fc311e108b532f /arch/arm64/kernel/signal.c | |
| parent | KVM: arm64: Kill 32-bit vCPUs on systems with mismatched EL0 support (diff) | |
| download | linux-dev-873c3e89777c8c56f936ae7aceca1a102aac6b9e.tar.xz linux-dev-873c3e89777c8c56f936ae7aceca1a102aac6b9e.zip | |
arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs
Scheduling a 32-bit application on a 64-bit-only CPU is a bad idea.
Ensure that 32-bit applications always take the slow-path when returning
to userspace on a system with mismatched support at EL0, so that we can
avoid trying to run on a 64-bit-only CPU and force a SIGKILL instead.
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210608180313.11502-5-will@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/kernel/signal.c')
| -rw-r--r-- | arch/arm64/kernel/signal.c | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index 6237486ff6bb..f8192f4ae0b8 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -911,6 +911,19 @@ static void do_signal(struct pt_regs *regs) restore_saved_sigmask(); } +static bool cpu_affinity_invalid(struct pt_regs *regs) +{ + if (!compat_user_mode(regs)) + return false; + + /* + * We're preemptible, but a reschedule will cause us to check the + * affinity again. + */ + return !cpumask_test_cpu(raw_smp_processor_id(), + system_32bit_el0_cpumask()); +} + asmlinkage void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags) { @@ -938,6 +951,19 @@ asmlinkage void do_notify_resume(struct pt_regs *regs, if (thread_flags & _TIF_NOTIFY_RESUME) { tracehook_notify_resume(regs); rseq_handle_notify_resume(NULL, regs); + + /* + * If we reschedule after checking the affinity + * then we must ensure that TIF_NOTIFY_RESUME + * is set so that we check the affinity again. + * Since tracehook_notify_resume() clears the + * flag, ensure that the compiler doesn't move + * it after the affinity check. + */ + barrier(); + + if (cpu_affinity_invalid(regs)) + force_sig(SIGKILL); } if (thread_flags & _TIF_FOREIGN_FPSTATE) |