Regression introduced by 16bd984557 and
5b177b3cab
The pre-computed absolute values used in encode_mcu_AC_first() and
encode_mcu_AC_refine() were stored in a JCOEF (signed short) array.
When attempting to losslessly transform a specially-crafted malformed
12-bit JPEG image with a coefficient value of -32768 into a progressive
12-bit JPEG image, the progressive Huffman encoder attempted to store
the absolute value of -32768 in the JCOEF array, thus overflowing the
16-bit signed data type. Therefore, at this point in the code:
8c5e78ce29/jcphuff.c (L889)
the absolute value was read as -32768, which caused the test at
8c5e78ce29/jcphuff.c (L896)
to fail, falling through to
8c5e78ce29/jcphuff.c (L908)
with an overly large value of r (46) that, when shifted left four
places, incremented, and passed to emit_symbol(), exceeded the maximum
index (255) for the derived code tables. Fortunately, the buffer
overrun was fully contained within phuff_entropy_encoder, so the issue
did not generate a segfault or other user-visible errant behavior, but
it did cause a UBSan failure that was detected by OSS-Fuzz.
This commit introduces an unsigned JCOEF (UJCOEF) data type and uses it
to store the absolute values of DCT coefficients computed by the
AC_first_prepare() and AC_refine_prepare() methods.
Note that the changes to the Arm Neon progressive Huffman encoder
extensions cause signed 16-bit instructions to be replaced with
equivalent unsigned 16-bit instructions, so the changes should be
performance-neutral.
Based on:
bbf61c0382Closes#628
... on platforms that support TLS, which should include all
currently-supported platforms
(https://libjpeg-turbo.org/Documentation/OfficialBinaries)
Addresses a concern raised in #87
Although it is still my opinion that the data race in init_simd() was
innocuous, we can now fix it for free thanks to
ae87a95861, so why not?
Modern Loongson processors are MIPS64-compatible, and MMI instructions
are now supported in the mainline of GCC. Thus, this commit adds
compile-time and run-time auto-detection of MMI instructions and moves
the MMI SIMD extensions for libjpeg-turbo from simd/loongson/ to
simd/mips64/. That will allow MMI and MSA instructions to co-exist
in the same build once #377 has been integrated.
Based on:
82953ddd61Closes#383
