acpi/nfit: Fix command-supported detection

The _DSM function number validation only happens to succeed when the
generic Linux command number translation corresponds with a
DSM-family-specific function number. This breaks NVDIMM-N
implementations that correctly implement _LSR, _LSW, and _LSI, but do
not happen to publish support for DSM function numbers 4, 5, and 6.

Recall that the support for _LS{I,R,W} family of methods results in the
DIMM being marked as supporting those command numbers at
acpi_nfit_register_dimms() time. The DSM function mask is only used for
ND_CMD_CALL support of non-NVDIMM_FAMILY_INTEL devices.

Fixes: 31eca76ba2 ("nfit, libnvdimm: limited/whitelisted dimm command...")
Cc: <stable@vger.kernel.org>
Link: https://github.com/pmem/ndctl/issues/78
Reported-by: Sujith Pandel <sujith_pandel@dell.com>
Tested-by: Sujith Pandel <sujith_pandel@dell.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/acpi/nfit/core.c

@@ -409,6 +409,32 @@ static bool payload_dumpable(struct nvdimm *nvdimm, unsigned int func)
 	return true;
 }
 
+static int cmd_to_func(struct nfit_mem *nfit_mem, unsigned int cmd,
+		struct nd_cmd_pkg *call_pkg)
+{
+	if (call_pkg) {
+		int i;
+
+		if (nfit_mem->family != call_pkg->nd_family)
+			return -ENOTTY;
+
+		for (i = 0; i < ARRAY_SIZE(call_pkg->nd_reserved2); i++)
+			if (call_pkg->nd_reserved2[i])
+				return -EINVAL;
+		return call_pkg->nd_command;
+	}
+
+	/* Linux ND commands == NVDIMM_FAMILY_INTEL function numbers */
+	if (nfit_mem->family == NVDIMM_FAMILY_INTEL)
+		return cmd;
+
+	/*
+	 * Force function number validation to fail since 0 is never
+	 * published as a valid function in dsm_mask.
+	 */
+	return 0;
+}
+
 int acpi_nfit_ctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
 		unsigned int cmd, void *buf, unsigned int buf_len, int *cmd_rc)
 {
@@ -422,30 +448,23 @@ int acpi_nfit_ctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
 	unsigned long cmd_mask, dsm_mask;
 	u32 offset, fw_status = 0;
 	acpi_handle handle;
-	unsigned int func;
 	const guid_t *guid;
-	int rc, i;
+	int func, rc, i;
 
 	if (cmd_rc)
 		*cmd_rc = -EINVAL;
-	func = cmd;
-	if (cmd == ND_CMD_CALL) {
-		call_pkg = buf;
-		func = call_pkg->nd_command;
-
-		for (i = 0; i < ARRAY_SIZE(call_pkg->nd_reserved2); i++)
-			if (call_pkg->nd_reserved2[i])
-				return -EINVAL;
-	}
 
 	if (nvdimm) {
 		struct acpi_device *adev = nfit_mem->adev;
 
 		if (!adev)
 			return -ENOTTY;
-		if (call_pkg && nfit_mem->family != call_pkg->nd_family)
-			return -ENOTTY;
 
+		if (cmd == ND_CMD_CALL)
+			call_pkg = buf;
+		func = cmd_to_func(nfit_mem, cmd, call_pkg);
+		if (func < 0)
+			return func;
 		dimm_name = nvdimm_name(nvdimm);
 		cmd_name = nvdimm_cmd_name(cmd);
 		cmd_mask = nvdimm_cmd_mask(nvdimm);
@@ -456,6 +475,7 @@ int acpi_nfit_ctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
 	} else {
 		struct acpi_device *adev = to_acpi_dev(acpi_desc);
 
+		func = cmd;
 		cmd_name = nvdimm_bus_cmd_name(cmd);
 		cmd_mask = nd_desc->cmd_mask;
 		dsm_mask = cmd_mask;
@@ -470,7 +490,13 @@ int acpi_nfit_ctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
 	if (!desc || (cmd && (desc->out_num + desc->in_num == 0)))
 		return -ENOTTY;
 
-	if (!test_bit(cmd, &cmd_mask) || !test_bit(func, &dsm_mask))
+	/*
+	 * Check for a valid command.  For ND_CMD_CALL, we also have to
+	 * make sure that the DSM function is supported.
+	 */
+	if (cmd == ND_CMD_CALL && !test_bit(func, &dsm_mask))
+		return -ENOTTY;
+	else if (!test_bit(cmd, &cmd_mask))
 		return -ENOTTY;
 
 	in_obj.type = ACPI_TYPE_PACKAGE;