Fix 32-bit overflow in LZW size calculation (MAX_CODE_LEN * lzwPos)#108
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uwezkhan wants to merge 2 commits intodloebl:mainfrom
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Fix 32-bit overflow in LZW size calculation (MAX_CODE_LEN * lzwPos)#108uwezkhan wants to merge 2 commits intodloebl:mainfrom
uwezkhan wants to merge 2 commits intodloebl:mainfrom
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This patch fixes a 32-bit arithmetic overflow in the LZW
byte list size calculations in cgif_raw.c.
The expression:
was evaluated using 32-bit arithmetic because
MAX_CODE_LEN is defined as an int and lzwPos is uint32_t.
Under C's usual arithmetic conversions, the multiplication
is performed as uint32_t before being widened to 64-bit
for the subsequent division.
If lzwPos is sufficiently large, the intermediate
32-bit multiplication can wrap around, resulting in an
incorrect (truncated) buffer size being passed to malloc().
The fix casts MAX_CODE_LEN to uint64_t:
This ensures the multiplication is performed in 64-bit
arithmetic and prevents intermediate overflow.
No API changes.
No behavioral changes for valid inputs.
Negligible runtime impact.