diff options
| author | Will Deacon | 2021-06-08 19:02:57 +0100 |
|---|---|---|
| committer | Will Deacon | 2021-06-11 13:25:41 +0100 |
| commit | 873c3e89777c8c56f936ae7aceca1a102aac6b9e (patch) | |
| tree | c84816eb04b65c9c89fe29e873fc311e108b532f /arch/arm64/kernel | |
| parent | 2f6a49bbc01da17867c26f6f650b1142e1d7c69d (diff) | |
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')
| -rw-r--r-- | arch/arm64/kernel/process.c | 19 | ||||
| -rw-r--r-- | arch/arm64/kernel/signal.c | 26 |
2 files changed, 44 insertions, 1 deletions
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index b4bb67f17a2c..f4a91bf1ce0c 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -527,6 +527,15 @@ static void erratum_1418040_thread_switch(struct task_struct *prev, write_sysreg(val, cntkctl_el1); } +static void compat_thread_switch(struct task_struct *next) +{ + if (!is_compat_thread(task_thread_info(next))) + return; + + if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) + set_tsk_thread_flag(next, TIF_NOTIFY_RESUME); +} + static void update_sctlr_el1(u64 sctlr) { /* @@ -568,6 +577,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, ssbs_thread_switch(next); erratum_1418040_thread_switch(prev, next); ptrauth_thread_switch_user(next); + compat_thread_switch(next); /* * Complete any pending TLB or cache maintenance on this CPU in case @@ -633,8 +643,15 @@ unsigned long arch_align_stack(unsigned long sp) */ void arch_setup_new_exec(void) { - current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0; + unsigned long mmflags = 0; + + if (is_compat_task()) { + mmflags = MMCF_AARCH32; + if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) + set_tsk_thread_flag(current, TIF_NOTIFY_RESUME); + } + current->mm->context.flags = mmflags; ptrauth_thread_init_user(); mte_thread_init_user(); 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) |