libnvdimm: fix integer overflow static analysis warning

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.

Cc: <stable@vger.kernel.org>
Fixes: 62232e45f4a2: "libnvdimm: control (ioctl) messages for nvdimm_bus..."
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
index a18c2914f4b6f3bea1583bcfcab8e1d6a5878b7a..66586ce23f1b176a984b8024ba2d3323f337fc07 100644 (file)
--- a/drivers/nvdimm/bus.c
+++ b/drivers/nvdimm/bus.c
@@ -911,19 +911,20 @@ static int __nd_ioctl(struct nvdimm_bus *nvdimm_bus, struct nvdimm *nvdimm,
                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);
@@ -983,7 +984,7 @@ static int __nd_ioctl(struct nvdimm_bus *nvdimm_bus, struct nvdimm *nvdimm,
 
        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);
 
@@ -1013,9 +1014,9 @@ static int __nd_ioctl(struct nvdimm_bus *nvdimm_bus, struct nvdimm *nvdimm,
                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,
                                ND_IOCTL_MAX_BUFLEN);
                return -EINVAL;