Fix GH-20964, GH-20927: fseek() stream seek with PHP_INT_MIN causes undefined behavior#21433
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iliaal wants to merge 1 commit intophp:masterfrom
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Fix GH-20964, GH-20927: fseek() stream seek with PHP_INT_MIN causes undefined behavior#21433iliaal wants to merge 1 commit intophp:masterfrom
iliaal wants to merge 1 commit intophp:masterfrom
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…fined behavior Negate after casting to unsigned instead of before, avoiding signed integer overflow when offset is ZEND_LONG_MIN. The same pattern existed in the pdo_sqlite and sqlite3 stream seek handlers. Closes phpGH-20964 Closes phpGH-20927
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Summary
Stream seek functions in memory, pdo_sqlite, and sqlite3 compute the absolute value of a negative offset using
(size_t)(-offset). Whenoffset == ZEND_LONG_MIN, the signed negation overflows -- undefined behavior caught by UBSAN.The fix swaps the cast order:
-(size_t)offsetcasts to unsigned first (well-defined), then negates (well-defined unsigned arithmetic). Same result for all values, no behavioral change.Files changed
main/streams/memory.c-- php://memory and php://temp stream seekext/pdo_sqlite/pdo_sqlite.c-- PDO SQLite blob stream seekext/sqlite3/sqlite3.c-- SQLite3 blob stream seekExisting PRs
This patch covers all three affected files.
Fixes #20964
Fixes #20927