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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Daniel Axtens <dja@axtens.net>
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Date: Fri, 15 Jan 2021 14:06:46 +1100
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Subject: [PATCH] video/readers/jpeg: Don't decode data before start of stream
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When a start of stream marker is encountered, we call grub_jpeg_decode_sos()
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which allocates space for a bitmap.
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When a restart marker is encountered, we call grub_jpeg_decode_data() which
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then fills in that bitmap.
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If we get a restart marker before the start of stream marker, we will
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attempt to write to a bitmap_ptr that hasn't been allocated. Catch this
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and bail out. This fixes an attempt to write to NULL.
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Signed-off-by: Daniel Axtens <dja@axtens.net>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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---
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grub-core/video/readers/jpeg.c | 4 ++++
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1 file changed, 4 insertions(+)
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diff --git a/grub-core/video/readers/jpeg.c b/grub-core/video/readers/jpeg.c
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index e5148120f..e31602f76 100644
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--- a/grub-core/video/readers/jpeg.c
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+++ b/grub-core/video/readers/jpeg.c
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@@ -646,6 +646,10 @@ grub_jpeg_decode_data (struct grub_jpeg_data *data)
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nr1 = (data->image_height + vb - 1) >> (3 + data->log_vs);
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nc1 = (data->image_width + hb - 1) >> (3 + data->log_hs);
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+ if (data->bitmap_ptr == NULL)
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+ return grub_error(GRUB_ERR_BAD_FILE_TYPE,
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+ "jpeg: attempted to decode data before start of stream");
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+
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for (; data->r1 < nr1 && (!data->dri || rst);
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data->r1++, data->bitmap_ptr += (vb * data->image_width - hb * nc1) * 3)
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for (c1 = 0; c1 < nc1 && (!data->dri || rst);
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