openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 270 insertions, 0 deletions

diff --git a/tools/perf/util/kvm-stat.c b/tools/perf/util/kvm-stat.c
new file mode 100644
index 000000000..755ab659a
--- /dev/null
+++ b/tools/perf/util/kvm-stat.c
@@ -0,0 +1,270 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "debug.h"
+#include "evsel.h"
+#include "kvm-stat.h"
+#include <dwarf-regs.h>
+
+bool kvm_exit_event(struct evsel *evsel)
+{
+	uint16_t e_machine = evsel__e_machine(evsel, /*e_flags=*/NULL);
+
+	return evsel__name_is(evsel, kvm_exit_trace(e_machine));
+}
+
+void exit_event_get_key(struct perf_sample *sample,
+			struct event_key *key)
+{
+	uint16_t e_machine = evsel__e_machine(sample->evsel, /*e_flags=*/NULL);
+
+	key->info = 0;
+	key->key  = perf_sample__intval(sample, kvm_exit_reason(e_machine));
+}
+
+
+bool exit_event_begin(struct perf_sample *sample, struct event_key *key)
+{
+	if (kvm_exit_event(sample->evsel)) {
+		exit_event_get_key(sample, key);
+		return true;
+	}
+
+	return false;
+}
+
+bool kvm_entry_event(struct evsel *evsel)
+{
+	uint16_t e_machine = evsel__e_machine(evsel, /*e_flags=*/NULL);
+
+	return evsel__name_is(evsel, kvm_entry_trace(e_machine));
+}
+
+bool exit_event_end(struct perf_sample *sample,
+		    struct event_key *key __maybe_unused)
+{
+	return kvm_entry_event(sample->evsel);
+}
+
+static const char *get_exit_reason(struct perf_kvm_stat *kvm,
+				   struct exit_reasons_table *tbl,
+				   u64 exit_code)
+{
+	while (tbl->reason != NULL) {
+		if (tbl->exit_code == exit_code)
+			return tbl->reason;
+		tbl++;
+	}
+
+	pr_err("unknown kvm exit code:%lld on %s\n",
+		(unsigned long long)exit_code, kvm->exit_reasons_isa);
+	return "UNKNOWN";
+}
+
+void exit_event_decode_key(struct perf_kvm_stat *kvm,
+			   struct event_key *key,
+			   char *decode)
+{
+	const char *exit_reason = get_exit_reason(kvm, key->exit_reasons,
+						  key->key);
+
+	scnprintf(decode, KVM_EVENT_NAME_LEN, "%s", exit_reason);
+}
+
+int setup_kvm_events_tp(struct perf_kvm_stat *kvm, uint16_t e_machine)
+{
+	switch (e_machine) {
+	case EM_PPC:
+	case EM_PPC64:
+		return __setup_kvm_events_tp_powerpc(kvm);
+	default:
+		return 0;
+	}
+}
+
+int cpu_isa_init(struct perf_kvm_stat *kvm, uint16_t e_machine, const char *cpuid)
+{
+	switch (e_machine) {
+	case EM_AARCH64:
+		return __cpu_isa_init_arm64(kvm);
+	case EM_LOONGARCH:
+		return __cpu_isa_init_loongarch(kvm);
+	case EM_PPC:
+	case EM_PPC64:
+		return __cpu_isa_init_powerpc(kvm);
+	case EM_RISCV:
+		return __cpu_isa_init_riscv(kvm);
+	case EM_S390:
+		return __cpu_isa_init_s390(kvm, cpuid);
+	case EM_X86_64:
+	case EM_386:
+		return __cpu_isa_init_x86(kvm, cpuid);
+	default:
+		pr_err("Unsupported kvm-stat host %d\n", e_machine);
+		return -1;
+	}
+}
+
+const char *vcpu_id_str(uint16_t e_machine)
+{
+	switch (e_machine) {
+	case EM_AARCH64:
+	case EM_RISCV:
+	case EM_S390:
+		return "id";
+	case EM_LOONGARCH:
+	case EM_PPC:
+	case EM_PPC64:
+	case EM_X86_64:
+	case EM_386:
+		return "vcpu_id";
+	default:
+		pr_err("Unsupported kvm-stat host %d\n", e_machine);
+		return NULL;
+	}
+}
+
+const char *kvm_exit_reason(uint16_t e_machine)
+{
+	switch (e_machine) {
+	case EM_AARCH64:
+		return "ret";
+	case EM_LOONGARCH:
+		return "reason";
+	case EM_PPC:
+	case EM_PPC64:
+		return "trap";
+	case EM_RISCV:
+		return "scause";
+	case EM_S390:
+		return "icptcode";
+	case EM_X86_64:
+	case EM_386:
+		return "exit_reason";
+	default:
+		pr_err("Unsupported kvm-stat host %d\n", e_machine);
+		return NULL;
+	}
+}
+
+const char *kvm_entry_trace(uint16_t e_machine)
+{
+	switch (e_machine) {
+	case EM_AARCH64:
+	case EM_RISCV:
+	case EM_X86_64:
+	case EM_386:
+		return "kvm:kvm_entry";
+	case EM_LOONGARCH:
+		return "kvm:kvm_enter";
+	case EM_PPC:
+	case EM_PPC64:
+		return "kvm_hv:kvm_guest_enter";
+	case EM_S390:
+		return "kvm:kvm_s390_sie_enter";
+	default:
+		pr_err("Unsupported kvm-stat host %d\n", e_machine);
+		return NULL;
+	}
+}
+
+const char *kvm_exit_trace(uint16_t e_machine)
+{
+	switch (e_machine) {
+	case EM_AARCH64:
+	case EM_LOONGARCH:
+	case EM_RISCV:
+	case EM_X86_64:
+	case EM_386:
+		return "kvm:kvm_exit";
+	case EM_PPC:
+	case EM_PPC64:
+		return "kvm_hv:kvm_guest_exit";
+	case EM_S390:
+		return "kvm:kvm_s390_sie_exit";
+	default:
+		pr_err("Unsupported kvm-stat host %d\n", e_machine);
+		return NULL;
+	}
+}
+
+const char * const *kvm_events_tp(uint16_t e_machine)
+{
+	switch (e_machine) {
+	case EM_AARCH64:
+		return __kvm_events_tp_arm64();
+	case EM_LOONGARCH:
+		return __kvm_events_tp_loongarch();
+	case EM_PPC:
+	case EM_PPC64:
+		return __kvm_events_tp_powerpc();
+	case EM_RISCV:
+		return __kvm_events_tp_riscv();
+	case EM_S390:
+		return __kvm_events_tp_s390();
+	case EM_X86_64:
+	case EM_386:
+		return __kvm_events_tp_x86();
+	default:
+		pr_err("Unsupported kvm-stat host %d\n", e_machine);
+		return NULL;
+	}
+}
+
+const struct kvm_reg_events_ops *kvm_reg_events_ops(uint16_t e_machine)
+{
+	switch (e_machine) {
+	case EM_AARCH64:
+		return __kvm_reg_events_ops_arm64();
+	case EM_LOONGARCH:
+		return __kvm_reg_events_ops_loongarch();
+	case EM_PPC:
+	case EM_PPC64:
+		return __kvm_reg_events_ops_powerpc();
+	case EM_RISCV:
+		return __kvm_reg_events_ops_riscv();
+	case EM_S390:
+		return __kvm_reg_events_ops_s390();
+	case EM_X86_64:
+	case EM_386:
+		return __kvm_reg_events_ops_x86();
+	default:
+		pr_err("Unsupported kvm-stat host %d\n", e_machine);
+		return NULL;
+	}
+}
+
+const char * const *kvm_skip_events(uint16_t e_machine)
+{
+	switch (e_machine) {
+	case EM_AARCH64:
+		return __kvm_skip_events_arm64();
+	case EM_LOONGARCH:
+		return __kvm_skip_events_loongarch();
+	case EM_PPC:
+	case EM_PPC64:
+		return __kvm_skip_events_powerpc();
+	case EM_RISCV:
+		return __kvm_skip_events_riscv();
+	case EM_S390:
+		return __kvm_skip_events_s390();
+	case EM_X86_64:
+	case EM_386:
+		return __kvm_skip_events_x86();
+	default:
+		pr_err("Unsupported kvm-stat host %d\n", e_machine);
+		return NULL;
+	}
+}
+
+int kvm_add_default_arch_event(uint16_t e_machine, int *argc, const char **argv)
+{
+	switch (e_machine) {
+	case EM_PPC:
+	case EM_PPC64:
+		return __kvm_add_default_arch_event_powerpc(argc, argv);
+	case EM_X86_64:
+	case EM_386:
+		return __kvm_add_default_arch_event_x86(argc, argv);
+	default:
+		return 0;
+	}
+}