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Diffstat (limited to '')
| -rw-r--r-- | debian/patches/0076-video-readers-jpeg-Block-int-underflow-wild-pointer-.patch | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/debian/patches/0076-video-readers-jpeg-Block-int-underflow-wild-pointer-.patch b/debian/patches/0076-video-readers-jpeg-Block-int-underflow-wild-pointer-.patch new file mode 100644 index 0000000..b292cbc --- /dev/null +++ b/debian/patches/0076-video-readers-jpeg-Block-int-underflow-wild-pointer-.patch @@ -0,0 +1,73 @@ +From a10c2350a766f9b315735931a49499a7e2c77bf3 Mon Sep 17 00:00:00 2001 +From: Daniel Axtens <dja@axtens.net> +Date: Wed, 7 Jul 2021 15:38:19 +1000 +Subject: video/readers/jpeg: Block int underflow -> wild pointer write + +Certain 1 px wide images caused a wild pointer write in +grub_jpeg_ycrcb_to_rgb(). This was caused because in grub_jpeg_decode_data(), +we have the following loop: + +for (; data->r1 < nr1 && (!data->dri || rst); + data->r1++, data->bitmap_ptr += (vb * data->image_width - hb * nc1) * 3) + +We did not check if vb * width >= hb * nc1. + +On a 64-bit platform, if that turns out to be negative, it will underflow, +be interpreted as unsigned 64-bit, then be added to the 64-bit pointer, so +we see data->bitmap_ptr jump, e.g.: + +0x6180_0000_0480 to +0x6181_0000_0498 + ^ + ~--- carry has occurred and this pointer is now far away from + any object. + +On a 32-bit platform, it will decrement the pointer, creating a pointer +that won't crash but will overwrite random data. + +Catch the underflow and error out. + +Fixes: CVE-2021-3697 + +Signed-off-by: Daniel Axtens <dja@axtens.net> +Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com> +--- + grub-core/video/readers/jpeg.c | 10 +++++++++- + 1 file changed, 9 insertions(+), 1 deletion(-) + +diff --git a/grub-core/video/readers/jpeg.c b/grub-core/video/readers/jpeg.c +index 1df1171d7..97a533b24 100644 +--- a/grub-core/video/readers/jpeg.c ++++ b/grub-core/video/readers/jpeg.c +@@ -23,6 +23,7 @@ + #include <grub/mm.h> + #include <grub/misc.h> + #include <grub/bufio.h> ++#include <grub/safemath.h> + + GRUB_MOD_LICENSE ("GPLv3+"); + +@@ -693,6 +694,7 @@ static grub_err_t + grub_jpeg_decode_data (struct grub_jpeg_data *data) + { + unsigned c1, vb, hb, nr1, nc1; ++ unsigned stride_a, stride_b, stride; + int rst = data->dri; + grub_err_t err = GRUB_ERR_NONE; + +@@ -705,8 +707,14 @@ grub_jpeg_decode_data (struct grub_jpeg_data *data) + return grub_error (GRUB_ERR_BAD_FILE_TYPE, + "jpeg: attempted to decode data before start of stream"); + ++ if (grub_mul(vb, data->image_width, &stride_a) || ++ grub_mul(hb, nc1, &stride_b) || ++ grub_sub(stride_a, stride_b, &stride)) ++ return grub_error (GRUB_ERR_BAD_FILE_TYPE, ++ "jpeg: cannot decode image with these dimensions"); ++ + for (; data->r1 < nr1 && (!data->dri || rst); +- data->r1++, data->bitmap_ptr += (vb * data->image_width - hb * nc1) * 3) ++ data->r1++, data->bitmap_ptr += stride * 3) + for (c1 = 0; c1 < nc1 && (!data->dri || rst); + c1++, rst--, data->bitmap_ptr += hb * 3) + { |