--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -1001,6 +1001,19 @@ config PPC_SECVAR_SYSFS
 	  read/write operations on these variables. Say Y if you have
 	  secure boot enabled and want to expose variables to userspace.
 
+config PPC_RTAS_FILTER
+	bool "Enable filtering of RTAS syscalls"
+	default y
+	depends on PPC_RTAS
+	help
+	  The RTAS syscall API has security issues that could be used to
+	  compromise system integrity. This option enforces restrictions on the
+	  RTAS calls and arguments passed by userspace programs to mitigate
+	  these issues.
+
+	  Say Y unless you know what you are doing and the filter is causing
+	  problems for you.
+
 endmenu
 
 config ISA_DMA_API
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -992,6 +992,147 @@ struct pseries_errorlog *get_pseries_err
 	return NULL;
 }
 
+#ifdef CONFIG_PPC_RTAS_FILTER
+
+/*
+ * The sys_rtas syscall, as originally designed, allows root to pass
+ * arbitrary physical addresses to RTAS calls. A number of RTAS calls
+ * can be abused to write to arbitrary memory and do other things that
+ * are potentially harmful to system integrity, and thus should only
+ * be used inside the kernel and not exposed to userspace.
+ *
+ * All known legitimate users of the sys_rtas syscall will only ever
+ * pass addresses that fall within the RMO buffer, and use a known
+ * subset of RTAS calls.
+ *
+ * Accordingly, we filter RTAS requests to check that the call is
+ * permitted, and that provided pointers fall within the RMO buffer.
+ * The rtas_filters list contains an entry for each permitted call,
+ * with the indexes of the parameters which are expected to contain
+ * addresses and sizes of buffers allocated inside the RMO buffer.
+ */
+struct rtas_filter {
+	const char *name;
+	int token;
+	/* Indexes into the args buffer, -1 if not used */
+	int buf_idx1;
+	int size_idx1;
+	int buf_idx2;
+	int size_idx2;
+
+	int fixed_size;
+};
+
+static struct rtas_filter rtas_filters[] __ro_after_init = {
+	{ "ibm,activate-firmware", -1, -1, -1, -1, -1 },
+	{ "ibm,configure-connector", -1, 0, -1, 1, -1, 4096 },	/* Special cased */
+	{ "display-character", -1, -1, -1, -1, -1 },
+	{ "ibm,display-message", -1, 0, -1, -1, -1 },
+	{ "ibm,errinjct", -1, 2, -1, -1, -1, 1024 },
+	{ "ibm,close-errinjct", -1, -1, -1, -1, -1 },
+	{ "ibm,open-errinct", -1, -1, -1, -1, -1 },
+	{ "ibm,get-config-addr-info2", -1, -1, -1, -1, -1 },
+	{ "ibm,get-dynamic-sensor-state", -1, 1, -1, -1, -1 },
+	{ "ibm,get-indices", -1, 2, 3, -1, -1 },
+	{ "get-power-level", -1, -1, -1, -1, -1 },
+	{ "get-sensor-state", -1, -1, -1, -1, -1 },
+	{ "ibm,get-system-parameter", -1, 1, 2, -1, -1 },
+	{ "get-time-of-day", -1, -1, -1, -1, -1 },
+	{ "ibm,get-vpd", -1, 0, -1, 1, 2 },
+	{ "ibm,lpar-perftools", -1, 2, 3, -1, -1 },
+	{ "ibm,platform-dump", -1, 4, 5, -1, -1 },
+	{ "ibm,read-slot-reset-state", -1, -1, -1, -1, -1 },
+	{ "ibm,scan-log-dump", -1, 0, 1, -1, -1 },
+	{ "ibm,set-dynamic-indicator", -1, 2, -1, -1, -1 },
+	{ "ibm,set-eeh-option", -1, -1, -1, -1, -1 },
+	{ "set-indicator", -1, -1, -1, -1, -1 },
+	{ "set-power-level", -1, -1, -1, -1, -1 },
+	{ "set-time-for-power-on", -1, -1, -1, -1, -1 },
+	{ "ibm,set-system-parameter", -1, 1, -1, -1, -1 },
+	{ "set-time-of-day", -1, -1, -1, -1, -1 },
+	{ "ibm,suspend-me", -1, -1, -1, -1, -1 },
+	{ "ibm,update-nodes", -1, 0, -1, -1, -1, 4096 },
+	{ "ibm,update-properties", -1, 0, -1, -1, -1, 4096 },
+	{ "ibm,physical-attestation", -1, 0, 1, -1, -1 },
+};
+
+static bool in_rmo_buf(u32 base, u32 end)
+{
+	return base >= rtas_rmo_buf &&
+		base < (rtas_rmo_buf + RTAS_RMOBUF_MAX) &&
+		base <= end &&
+		end >= rtas_rmo_buf &&
+		end < (rtas_rmo_buf + RTAS_RMOBUF_MAX);
+}
+
+static bool block_rtas_call(int token, int nargs,
+			    struct rtas_args *args)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(rtas_filters); i++) {
+		struct rtas_filter *f = &rtas_filters[i];
+		u32 base, size, end;
+
+		if (token != f->token)
+			continue;
+
+		if (f->buf_idx1 != -1) {
+			base = be32_to_cpu(args->args[f->buf_idx1]);
+			if (f->size_idx1 != -1)
+				size = be32_to_cpu(args->args[f->size_idx1]);
+			else if (f->fixed_size)
+				size = f->fixed_size;
+			else
+				size = 1;
+
+			end = base + size - 1;
+			if (!in_rmo_buf(base, end))
+				goto err;
+		}
+
+		if (f->buf_idx2 != -1) {
+			base = be32_to_cpu(args->args[f->buf_idx2]);
+			if (f->size_idx2 != -1)
+				size = be32_to_cpu(args->args[f->size_idx2]);
+			else if (f->fixed_size)
+				size = f->fixed_size;
+			else
+				size = 1;
+			end = base + size - 1;
+
+			/*
+			 * Special case for ibm,configure-connector where the
+			 * address can be 0
+			 */
+			if (!strcmp(f->name, "ibm,configure-connector") &&
+			    base == 0)
+				return false;
+
+			if (!in_rmo_buf(base, end))
+				goto err;
+		}
+
+		return false;
+	}
+
+err:
+	pr_err_ratelimited("sys_rtas: RTAS call blocked - exploit attempt?\n");
+	pr_err_ratelimited("sys_rtas: token=0x%x, nargs=%d (called by %s)\n",
+			   token, nargs, current->comm);
+	return true;
+}
+
+#else
+
+static bool block_rtas_call(int token, int nargs,
+			    struct rtas_args *args)
+{
+	return false;
+}
+
+#endif /* CONFIG_PPC_RTAS_FILTER */
+
 /* We assume to be passed big endian arguments */
 SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
 {
@@ -1029,6 +1170,9 @@ SYSCALL_DEFINE1(rtas, struct rtas_args _
 	args.rets = &args.args[nargs];
 	memset(args.rets, 0, nret * sizeof(rtas_arg_t));
 
+	if (block_rtas_call(token, nargs, &args))
+		return -EINVAL;
+
 	/* Need to handle ibm,suspend_me call specially */
 	if (token == ibm_suspend_me_token) {
 
@@ -1090,6 +1234,9 @@ void __init rtas_initialize(void)
 	unsigned long rtas_region = RTAS_INSTANTIATE_MAX;
 	u32 base, size, entry;
 	int no_base, no_size, no_entry;
+#ifdef CONFIG_PPC_RTAS_FILTER
+	int i;
+#endif
 
 	/* Get RTAS dev node and fill up our "rtas" structure with infos
 	 * about it.
@@ -1129,6 +1276,12 @@ void __init rtas_initialize(void)
 #ifdef CONFIG_RTAS_ERROR_LOGGING
 	rtas_last_error_token = rtas_token("rtas-last-error");
 #endif
+
+#ifdef CONFIG_PPC_RTAS_FILTER
+	for (i = 0; i < ARRAY_SIZE(rtas_filters); i++) {
+		rtas_filters[i].token = rtas_token(rtas_filters[i].name);
+	}
+#endif
 }
 
 int __init early_init_dt_scan_rtas(unsigned long node,
