From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Daniel Axtens Date: Fri, 15 Jan 2021 14:06:46 +1100 Subject: [PATCH] video/readers/jpeg: Don't decode data before start of stream When a start of stream marker is encountered, we call grub_jpeg_decode_sos() which allocates space for a bitmap. When a restart marker is encountered, we call grub_jpeg_decode_data() which then fills in that bitmap. If we get a restart marker before the start of stream marker, we will attempt to write to a bitmap_ptr that hasn't been allocated. Catch this and bail out. This fixes an attempt to write to NULL. Signed-off-by: Daniel Axtens Reviewed-by: Daniel Kiper --- grub-core/video/readers/jpeg.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/grub-core/video/readers/jpeg.c b/grub-core/video/readers/jpeg.c index 28c1d62515e..c48cbd41b48 100644 --- a/grub-core/video/readers/jpeg.c +++ b/grub-core/video/readers/jpeg.c @@ -646,6 +646,10 @@ grub_jpeg_decode_data (struct grub_jpeg_data *data) nr1 = (data->image_height + vb - 1) >> (3 + data->log_vs); nc1 = (data->image_width + hb - 1) >> (3 + data->log_hs); + if (data->bitmap_ptr == NULL) + return grub_error(GRUB_ERR_BAD_FILE_TYPE, + "jpeg: attempted to decode data before start of stream"); + for (; data->r1 < nr1 && (!data->dri || rst); data->r1++, data->bitmap_ptr += (vb * data->image_width - hb * nc1) * 3) for (c1 = 0; c1 < nc1 && (!data->dri || rst);