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Lossless decomp: Range-limit 12-bit samples

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12-bit is the only data precision for which the range of the sample data
type exceeds the valid sample range, so it is possible to craft a 12-bit
lossless JPEG image that contains out-of-range 12-bit samples.
Attempting to decompress such an image using color quantization or merged
upsampling (NOTE: libjpeg-turbo cannot generate YCbCr or subsampled
lossless JPEG images, but it can decompress them) caused segfaults or
buffer overruns when those algorithms attempted to use the out-of-range
sample values as array indices.  This commit modifies the lossless
decompressor so that it range-limits the output of the scaler when using
12-bit samples.

Fixes #670
Fixes #672
Fixes #673
Fixes #674
Fixes #675
Fixes #676
Fixes #677
Fixes #678
Fixes #679
Fixes #681
Fixes #683
This commit is contained in:
DRC
2023-04-04 13:53:21 -05:00
parent 3f43c6a310
commit 9f756bc67a
2 changed files with 20 additions and 1 deletions
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ChangeLog.md
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@@ -8,6 +8,13 @@ subsampling, which allows losslessly transposed or rotated 4:1:1 JPEG images to
be losslessly cropped, partially decompressed, or decompressed to planar YUV
images.
2. Fixed various segfaults and buffer overruns that occurred when attempting to
decompress various specially-crafted malformed 12-bit-per-component lossless
JPEG images. These issues were caused by out-of-range sample values that were
not range-limited before being used as array indices. The issues were specific
to 12-bit data precision, since that is the only data precision for which the
range of the sample data type exceeds the valid sample range.
2.1.91 (3.0 beta2)
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