Orangefs: add verification to decode_dirents

Also add comments to decode_dirents and make it more readable.

Signed-off-by: Mike Marshall <hubcap@omnibond.com>

1 files changed, 93 insertions, 25 deletions

diff --git a/fs/orangefs/dir.c b/fs/orangefs/dir.c
index 58558e37fb8a..6f5836d6a7a3 100644
--- a/fs/orangefs/dir.c
+++ b/fs/orangefs/dir.c
@@ -15,7 +15,14 @@ struct readdir_handle_s {
 };
 
 /*
- * decode routine needed by kmod to make sense of the shared page for readdirs.
+ * decode routine used by kmod to deal with the blob sent from
+ * userspace for readdirs. The blob contains zero or more of these
+ * sub-blobs:
+ *   __u32 - represents length of the character string that follows.
+ *   string - between 1 and ORANGEFS_NAME_MAX bytes long.
+ *   padding - (if needed) to cause the __u32 plus the string to be
+ *             eight byte aligned.
+ *   khandle - sizeof(khandle) bytes.
  */
 static long decode_dirents(char *ptr, size_t size,
                            struct orangefs_readdir_response_s *readdir)
@@ -24,54 +31,115 @@ static long decode_dirents(char *ptr, size_t size,
         struct orangefs_readdir_response_s *rd =
                 (struct orangefs_readdir_response_s *) ptr;
         char *buf = ptr;
+        int khandle_size = sizeof(struct orangefs_khandle);
+        size_t offset = offsetof(struct orangefs_readdir_response_s,
+                                dirent_array);
+        /* 8 reflects eight byte alignment */
+        int smallest_blob = khandle_size + 8;
+        __u32 len;
+        int aligned_len;
+        int sizeof_u32 = sizeof(__u32);
+        long ret;
 
-        if (size < offsetof(struct orangefs_readdir_response_s, dirent_array))
-                return -EINVAL;
+        gossip_debug(GOSSIP_DIR_DEBUG, "%s: size:%zu:\n", __func__, size);
+
+        /* size is = offset on empty dirs, > offset on non-empty dirs... */
+        if (size < offset) {
+                gossip_err("%s: size:%zu: offset:%zu:\n",
+                           __func__,
+                           size,
+                           offset);
+                ret = -EINVAL;
+                goto out;
+        }
+
+        if ((size == offset) && (readdir->orangefs_dirent_outcount != 0)) {
+                gossip_err("%s: size:%zu: dirent_outcount:%d:\n",
+                           __func__,
+                           size,
+                           readdir->orangefs_dirent_outcount);
+                ret = -EINVAL;
+                goto out;
+        }
 
         readdir->token = rd->token;
         readdir->orangefs_dirent_outcount = rd->orangefs_dirent_outcount;
         readdir->dirent_array = kcalloc(readdir->orangefs_dirent_outcount,
                                         sizeof(*readdir->dirent_array),
                                         GFP_KERNEL);
-        if (readdir->dirent_array == NULL)
-                return -ENOMEM;
+        if (readdir->dirent_array == NULL) {
+                gossip_err("%s: kcalloc failed.\n", __func__);
+                ret = -ENOMEM;
+                goto out;
+        }
 
-        buf += offsetof(struct orangefs_readdir_response_s, dirent_array);
-        size -= offsetof(struct orangefs_readdir_response_s, dirent_array);
+        buf += offset;
+        size -= offset;
 
         for (i = 0; i < readdir->orangefs_dirent_outcount; i++) {
-                __u32 len;
-
-                if (size < 4)
-                        goto Einval;
+                if (size < smallest_blob) {
+                        gossip_err("%s: size:%zu: smallest_blob:%d:\n",
+                                   __func__,
+                                   size,
+                                   smallest_blob);
+                        ret = -EINVAL;
+                        goto free;
+                }
 
                 len = *(__u32 *)buf;
-                if (len >= (unsigned)-24)
-                        goto Einval;
+                if ((len < 1) || (len > ORANGEFS_NAME_MAX)) {
+                        gossip_err("%s: len:%d:\n", __func__, len);
+                        ret = -EINVAL;
+                        goto free;
+                }
 
-                readdir->dirent_array[i].d_name = buf + 4;
+                gossip_debug(GOSSIP_DIR_DEBUG,
+                             "%s: size:%zu: len:%d:\n",
+                             __func__,
+                             size,
+                             len);
+
+                readdir->dirent_array[i].d_name = buf + sizeof_u32;
                 readdir->dirent_array[i].d_length = len;
 
                 /*
-                 * Round 4 + len + 1, which is the encoded size plus the string
-                 * plus the null terminator to the nearest eight byte boundry.
+                 * Calculate "aligned" length of this string and its
+                 * associated __u32 descriptor.
                  */
-                len = ((4 + len + 1) + 7) & ~7;
-                if (size < len + 16)
-                        goto Einval;
-                size -= len + 16;
+                aligned_len = ((sizeof_u32 + len + 1) + 7) & ~7;
+                gossip_debug(GOSSIP_DIR_DEBUG,
+                             "%s: aligned_len:%d:\n",
+                             __func__,
+                             aligned_len);
 
-                buf += len;
+                /*
+                 * The end of the blob should coincide with the end
+                 * of the last sub-blob.
+                 */
+                if (size < aligned_len + khandle_size) {
+                        gossip_err("%s: ran off the end of the blob.\n",
+                                   __func__);
+                        ret = -EINVAL;
+                        goto free;
+                }
+                size -= aligned_len + khandle_size;
+
+                buf += aligned_len;
 
                 readdir->dirent_array[i].khandle =
                         *(struct orangefs_khandle *) buf;
-                buf += 16;
+                buf += khandle_size;
         }
-        return buf - ptr;
-Einval:
+        ret = buf - ptr;
+        gossip_debug(GOSSIP_DIR_DEBUG, "%s: returning:%ld:\n", __func__, ret);
+        goto out;
+
+free:
         kfree(readdir->dirent_array);
         readdir->dirent_array = NULL;
-        return -EINVAL;
+
+out:
+        return ret;
 }
 
 static long readdir_handle_ctor(struct readdir_handle_s *rhandle, void *buf,