fix(pngimage): correct 16-bit sBIT handling in compare_read - #914
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Samin061 wants to merge 1 commit into
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fix(pngimage): correct 16-bit sBIT handling in compare_read#914Samin061 wants to merge 1 commit into
Samin061 wants to merge 1 commit into
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compare_read fills sig_bits with one entry per colour component, but for 16-bit images the sBIT check looped once per byte and the big-endian expansion wrote sig_bits[2*b+1]/[2*b+0] starting from b == channels. A 16-bit RGBA image with an sBIT chunk drives b to 4 and stores two bytes past the 8-byte sig_bits array. Bound the check by the component count and expand into sig_bits[2*b-1]/[2*b-2] from sig_bits[b-1].
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The change on line 1162 makes no sense whatsoever; 'b' is incremented. The change is also isolated from the rest of the changes; it is located within a separate loop. The other change implies an off-by-one error but the explanation is utterly unrelated. This looks to me like something generated by an AI. I'm not paid to train AIs so I will not comment further. |
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compare_read fills sig_bits with one entry per colour component, but for 16-bit images the sBIT sanity check loops once per byte and the case 16 expansion writes sig_bits[2b+1]/[2b+0] starting from b == channels. Feeding pngimage a 16-bit RGBA file that carries an sBIT chunk drives b to 4, storing two bytes past the 8-byte sig_bits stack array; AddressSanitizer reports a stack-buffer-overflow at the write. Bound the check by the real component count and expand into sig_bits[2b-1]/[2b-2] from sig_bits[b-1] so the eight bytes are produced within the array.