Prevent unsigned overflow in php_handle_swc() #17678
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The multiplication of `ZSTR_LEN(bufz)` with the `factor` can easily overflow on LLP64 architectures, causing a smaller `buf` to be allocated than expected. While there are no security implications, calling `uncompress()` with the small buffer cannot be successful (`Z_BUF_ERROR`). We avoid such superfluous calls by bailing out of the loop early in case of an overflow condition. Note that `safe_emalloc()` would not help here, since that will not prevent 32bit unsigned overflow on 64bit architectures.
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The multiplication of
ZSTR_LEN(bufz)with thefactorcan easily overflow on LLP64 architectures, causing a smallerbufto be allocated than expected. While there are no security implications, callinguncompress()with the small buffer cannot be successful (Z_BUF_ERROR). We avoid such superfluous calls by bailing out of the loop early in case of an overflow condition.Note that
safe_emalloc()would not help here, since that will not prevent 32bit unsigned overflow on 64bit architectures.