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-rw-r--r--arch/powerpc/kernel/rtas.c153
1 files changed, 153 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 806d554ce357..954f41676f69 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -992,6 +992,147 @@ struct pseries_errorlog *get_pseries_errorlog(struct rtas_error_log *log,
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 __user *, uargs)
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,