[PATCH] ACPI: NFIT: prevent underflow in acpi_nfit_ctl(

[Dan Carpenter <error27@gmail.com>]

The concern here would be that "family" is negative and we pass a
negative value to test_bit() resulting in an out of bounds read
and potentially a crash.

This patch is based on static analysis and not on testing.

Fixes: 9a7e3d7f0568 ("ACPI: NFIT: Fix input validation of bus-family")
Signed-off-by: Dan Carpenter <error27@gmail.com>
---
Another idea would be that we could change test_bit() to not accept
bits higher than INT_MAX.

 drivers/acpi/nfit/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index f1cc5ec6a3b6..da0739f04c98 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -446,10 +446,10 @@ int acpi_nfit_ctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
 	const char *cmd_name, *dimm_name;
 	unsigned long cmd_mask, dsm_mask;
 	u32 offset, fw_status = 0;
+	unsigned int family = 0;
 	acpi_handle handle;
 	const guid_t *guid;
 	int func, rc, i;
-	int family = 0;
 
 	if (cmd_rc)
 		*cmd_rc = -EINVAL;
-- 
2.35.1