[PATCH AUTOSEL 4.9 20/21] libnvdimm: Out of bounds read in __nd_ioctl()

[Sasha Levin]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

[ Upstream commit f84afbdd3a9e5e10633695677b95422572f920dc ]

The "cmd" comes from the user and it can be up to 255.  It it's more
than the number of bits in long, it results out of bounds read when we
check test_bit(cmd, &cmd_mask).  The highest valid value for "cmd" is
ND_CMD_CALL (10) so I added a compare against that.

Fixes: 62232e45f4a2 ("libnvdimm: control (ioctl) messages for nvdimm_bus and nvdimm devices")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200225162055.amtosfy7m35aivxg@xxxxxxxxxxxxx
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/nvdimm/bus.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
index 5768a4749564a..65ac1d3870f93 100644
--- a/drivers/nvdimm/bus.c
+++ b/drivers/nvdimm/bus.c
@@ -851,8 +851,10 @@ static int __nd_ioctl(struct nvdimm_bus *nvdimm_bus, struct nvdimm *nvdimm,
 			return -EFAULT;
 	}
 
-	if (!desc || (desc->out_num + desc->in_num == 0) ||
-			!test_bit(cmd, &cmd_mask))
+	if (!desc ||
+	    (desc->out_num + desc->in_num == 0) ||
+	    cmd > ND_CMD_CALL ||
+	    !test_bit(cmd, &cmd_mask))
 		return -ENOTTY;
 
 	/* fail write commands (when read-only) */
-- 
2.20.1