ntfs-3g_apply.c: handle ntfs_attr_pwrite() short writes

diff --git a/src/ntfs-3g_apply.c b/src/ntfs-3g_apply.c
index 23ffe2860ea33abfc6271a8902a45de7853031a8..d0f3bb6cc86b0b850e43e7547cf5e2fb936824ed 100644 (file)
--- a/src/ntfs-3g_apply.c
+++ b/src/ntfs-3g_apply.c
@@ -855,16 +855,35 @@ out:
        return ret;
 }
 
+/* Note: contrary to its documentation, ntfs_attr_pwrite() can return a short
+ * count in non-error cases --- specifically, when writing to a compressed
+ * attribute and the requested count exceeds the size of an NTFS "compression
+ * block".  Therefore, we must continue calling ntfs_attr_pwrite() until all
+ * bytes have been written or a real error has occurred.  */
+static bool
+ntfs_3g_full_pwrite(ntfs_attr *na, u64 offset, size_t size, const u8 *data)
+{
+       while (size) {
+               s64 res = ntfs_attr_pwrite(na, offset, size, data);
+               if (unlikely(res <= 0))
+                       return false;
+               wimlib_assert(res <= size);
+               offset += res;
+               size -= res;
+               data += res;
+       }
+       return true;
+}
+
 static int
 ntfs_3g_extract_chunk(const void *chunk, size_t size, void *_ctx)
 {
        struct ntfs_3g_apply_ctx *ctx = _ctx;
-       s64 res;
 
        for (unsigned i = 0; i < ctx->num_open_attrs; i++) {
-               res = ntfs_attr_pwrite(ctx->open_attrs[i],
-                                      ctx->offset, size, chunk);
-               if (res != size) {
+               if (!ntfs_3g_full_pwrite(ctx->open_attrs[i],
+                                        ctx->offset, size, chunk))
+               {
                        ERROR_WITH_ERRNO("Error writing data to NTFS volume");
                        return WIMLIB_ERR_NTFS_3G;
                }