Replace use of blobmsg_check_attr by blobmsg_check_attr_len

blobmsg_check_attr_len adds a length limit specifying the max offset
from attr that can be read safely.

Signed-off-by: Tobias Schramm <tobleminer@gmail.com>
[rebased and reworked, line wrapped commit message, _safe -> _len]
Signed-off-by: Petr Štetiar <ynezz@true.cz>

diff --git a/blobmsg.c b/blobmsg.c
index 71d4a36a647cb7ac7bac01c6f79833fd3614d4a8..fbc6d2de9135509a955fd55d43a2e0b6be01fe4a 100644 (file)
--- a/blobmsg.c
+++ b/blobmsg.c
@@ -33,38 +33,70 @@ blobmsg_namelen(const struct blobmsg_hdr *hdr)
 
 bool blobmsg_check_attr(const struct blob_attr *attr, bool name)
 {
+       return blobmsg_check_attr_len(attr, name, blob_raw_len(attr));
+}
+
+static bool blobmsg_check_name(const struct blob_attr *attr, size_t len, bool name)
+{
+       char *limit = (char *) attr + len;
        const struct blobmsg_hdr *hdr;
-       const char *data;
-       size_t len;
-       int id;
 
-       if (blob_len(attr) < sizeof(struct blobmsg_hdr))
+       hdr = blob_data(attr);
+       if (name && !hdr->namelen)
                return false;
 
-       hdr = (void *) attr->data;
-       if (!hdr->namelen && name)
+       if ((char *) hdr->name + blobmsg_namelen(hdr) > limit)
                return false;
 
-       if (blobmsg_namelen(hdr) > blob_len(attr) - sizeof(struct blobmsg_hdr))
+       if (blobmsg_namelen(hdr) > (blob_len(attr) - sizeof(struct blobmsg_hdr)))
                return false;
 
        if (hdr->name[blobmsg_namelen(hdr)] != 0)
                return false;
 
-       id = blob_id(attr);
-       len = blobmsg_data_len(attr);
-       if (len > blob_raw_len(attr))
-               return false;
+       return true;
+}
+
+static const char* blobmsg_check_data(const struct blob_attr *attr, size_t len, size_t *data_len)
+{
+       char *limit = (char *) attr + len;
+       const char *data;
+
+       *data_len = blobmsg_data_len(attr);
+       if (*data_len > blob_raw_len(attr))
+               return NULL;
 
        data = blobmsg_data(attr);
+       if (data + *data_len > limit)
+               return NULL;
+
+       return data;
+}
+
+bool blobmsg_check_attr_len(const struct blob_attr *attr, bool name, size_t len)
+{
+       const char *data;
+       size_t data_len;
+       int id;
 
+       if (len < sizeof(struct blob_attr))
+               return false;
+
+       if (!blobmsg_check_name(attr, len, name))
+               return false;
+
+       id = blob_id(attr);
        if (id > BLOBMSG_TYPE_LAST)
                return false;
 
        if (!blob_type[id])
                return true;
 
-       return blob_check_type(data, len, blob_type[id]);
+       data = blobmsg_check_data(attr, len, &data_len);
+       if (!data)
+               return false;
+
+       return blob_check_type(data, data_len, blob_type[id]);
 }
 
 int blobmsg_check_array(const struct blob_attr *attr, int type)
@@ -115,7 +147,7 @@ int blobmsg_parse_array(const struct blobmsg_policy *policy, int policy_len,
                    blob_id(attr) != policy[i].type)
                        continue;
 
-               if (!blobmsg_check_attr(attr, false))
+               if (!blobmsg_check_attr_len(attr, false, len))
                        return -1;
 
                if (tb[i])
@@ -162,7 +194,7 @@ int blobmsg_parse(const struct blobmsg_policy *policy, int policy_len,
                        if (blobmsg_namelen(hdr) != pslen[i])
                                continue;
 
-                       if (!blobmsg_check_attr(attr, true))
+                       if (!blobmsg_check_attr_len(attr, true, len))
                                return -1;
 
                        if (tb[i])

diff --git a/blobmsg.h b/blobmsg.h
index 00e0fdc1d5c65dce44c11e92eefdb1aaa935b856..c44015942a378c53a69df1cfdcd7c06c4332ed5f 100644 (file)
--- a/blobmsg.h
+++ b/blobmsg.h
@@ -107,6 +107,8 @@ static inline size_t blobmsg_len(const struct blob_attr *attr)
 bool blobmsg_check_attr(const struct blob_attr *attr, bool name);
 bool blobmsg_check_attr_list(const struct blob_attr *attr, int type);
 
+bool blobmsg_check_attr_len(const struct blob_attr *attr, bool name, size_t len);
+
 /*
  * blobmsg_check_array: validate array/table and return size
  *