[PATCH 4.13 25/52] libnvdimm: fix integer overflow static analysis warning

From: Greg Kroah-Hartman
Date: Mon Sep 18 2017 - 05:56:24 EST

4.13-stable review patch. If anyone has any objections, please let me know.


From: Dan Williams <dan.j.williams@xxxxxxxxx>

commit 58738c495e15badd2015e19ff41f1f1ed55200bc upstream.

Dan reports:
The patch 62232e45f4a2: "libnvdimm: control (ioctl) messages for
nvdimm_bus and nvdimm devices" from Jun 8, 2015, leads to the
following static checker warning:

drivers/nvdimm/bus.c:1018 __nd_ioctl()
warn: integer overflows 'buf_len'

From a casual review, this seems like it might be a real bug. On
the first iteration we load some data into in_env[]. On the second
iteration we read a use controlled "in_size" from nd_cmd_in_size().
It can go up to UINT_MAX - 1. A high number means we will fill the
whole in_env[] buffer. But we potentially keep looping and adding
more to in_len so now it can be any value.

It simple enough to change, but it feels weird that we keep looping
even though in_env is totally full. Shouldn't we just return an
error if we don't have space for desc->in_num.

We keep looping because the size of the total input is allowed to be
bigger than the 'envelope' which is a subset of the payload that tells
us how much data to expect. For safety explicitly check that buf_len
does not overflow which is what the checker flagged.

Fixes: 62232e45f4a2: "libnvdimm: control (ioctl) messages for nvdimm_bus..."
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/nvdimm/bus.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)

--- a/drivers/nvdimm/bus.c
+++ b/drivers/nvdimm/bus.c
@@ -905,19 +905,20 @@ static int __nd_ioctl(struct nvdimm_bus
int read_only, unsigned int ioctl_cmd, unsigned long arg)
struct nvdimm_bus_descriptor *nd_desc = nvdimm_bus->nd_desc;
- size_t buf_len = 0, in_len = 0, out_len = 0;
static char out_env[ND_CMD_MAX_ENVELOPE];
static char in_env[ND_CMD_MAX_ENVELOPE];
const struct nd_cmd_desc *desc = NULL;
unsigned int cmd = _IOC_NR(ioctl_cmd);
- unsigned int func = cmd;
- void __user *p = (void __user *) arg;
struct device *dev = &nvdimm_bus->dev;
- struct nd_cmd_pkg pkg;
+ void __user *p = (void __user *) arg;
const char *cmd_name, *dimm_name;
+ u32 in_len = 0, out_len = 0;
+ unsigned int func = cmd;
unsigned long cmd_mask;
- void *buf;
+ struct nd_cmd_pkg pkg;
int rc, i, cmd_rc;
+ u64 buf_len = 0;
+ void *buf;

if (nvdimm) {
desc = nd_cmd_dimm_desc(cmd);
@@ -977,7 +978,7 @@ static int __nd_ioctl(struct nvdimm_bus

if (cmd == ND_CMD_CALL) {
func = pkg.nd_command;
- dev_dbg(dev, "%s:%s, idx: %llu, in: %zu, out: %zu, len %zu\n",
+ dev_dbg(dev, "%s:%s, idx: %llu, in: %u, out: %u, len %llu\n",
__func__, dimm_name, pkg.nd_command,
in_len, out_len, buf_len);

@@ -1007,9 +1008,9 @@ static int __nd_ioctl(struct nvdimm_bus
out_len += out_size;

- buf_len = out_len + in_len;
+ buf_len = (u64) out_len + (u64) in_len;
if (buf_len > ND_IOCTL_MAX_BUFLEN) {
- dev_dbg(dev, "%s:%s cmd: %s buf_len: %zu > %d\n", __func__,
+ dev_dbg(dev, "%s:%s cmd: %s buf_len: %llu > %d\n", __func__,
dimm_name, cmd_name, buf_len,
return -EINVAL;