[PATCH] acpi: nfit: fix narrowing conversion in acpi_nfit_ctl

[Murad Masimov]

Syzkaller has reported a warning in to_nfit_bus_uuid(): "only secondary
bus families can be translated". This warning is emited if the argument
is equal to NVDIMM_BUS_FAMILY_NFIT == 0. Function acpi_nfit_ctl() first
verifies that a user-provided value call_pkg->nd_family of type u64 is
not equal to 0. Then the value is converted to int, and only after that
is compared to NVDIMM_BUS_FAMILY_MAX. This can lead to passing an invalid
argument to acpi_nfit_ctl(), if call_pkg->nd_family is non-zero, while
the lower 32 bits are zero.

All checks of the input value should be applied to the original variable
call_pkg->nd_family.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 6450ddbd5d8e ("ACPI: NFIT: Define runtime firmware activation commands")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: syzbot+c80d8dc0d9fa81a3cd8c@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=c80d8dc0d9fa81a3cd8c
Signed-off-by: Murad Masimov <m.masimov@xxxxxxxxxxxxxxxxx>
---
 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 a5d47819b3a4..ae035b93da08 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -485,7 +485,7 @@ int acpi_nfit_ctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
 		cmd_mask = nd_desc->cmd_mask;
 		if (cmd == ND_CMD_CALL && call_pkg->nd_family) {
 			family = call_pkg->nd_family;
-			if (family > NVDIMM_BUS_FAMILY_MAX ||
+			if (call_pkg->nd_family > NVDIMM_BUS_FAMILY_MAX ||
 			    !test_bit(family, &nd_desc->bus_family_mask))
 				return -EINVAL;
 			family = array_index_nospec(family,
--
2.39.2