--- a/libavcodec/v4l2_m2m_enc.c
+++ b/libavcodec/v4l2_m2m_enc.c
@@ -338,6 +338,7 @@
     V4L2m2mPriv *priv = avctx->priv_data;
     enum AVPixelFormat pix_fmt_output;
     uint32_t v4l2_fmt_output;
+    unsigned int output_width, output_height;
     int ret;
 
     ret = ff_v4l2_m2m_create_context(priv, &s);
@@ -370,6 +371,25 @@
         v4l2_fmt_output = output->format.fmt.pix_mp.pixelformat;
     else
         v4l2_fmt_output = output->format.fmt.pix.pixelformat;
+
+    /* Drivers may clamp the requested raw format to their supported size.
+     * The software-frame upload still uses avctx/frame dimensions, so a
+     * smaller negotiated format would overrun the mapped output buffers.
+     * Allow upward alignment, but reject frames that do not fit.
+     */
+    if (V4L2_TYPE_IS_MULTIPLANAR(output->type)) {
+        output_width  = output->format.fmt.pix_mp.width;
+        output_height = output->format.fmt.pix_mp.height;
+    } else {
+        output_width  = output->format.fmt.pix.width;
+        output_height = output->format.fmt.pix.height;
+    }
+    if (output_width < avctx->width || output_height < avctx->height) {
+        av_log(avctx, AV_LOG_ERROR,
+               "Encoder cannot fit requested %dx%d frame in negotiated %ux%u format\n",
+               avctx->width, avctx->height, output_width, output_height);
+        return AVERROR(EINVAL);
+    }
 
     pix_fmt_output = ff_v4l2_format_v4l2_to_avfmt(v4l2_fmt_output, AV_CODEC_ID_RAWVIDEO);
     if (pix_fmt_output != avctx->pix_fmt) {