Fix use-after-free on re-entrant ftp_close() during a transfer#118
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Fix use-after-free on re-entrant ftp_close() during a transfer#118iliaal wants to merge 1 commit into
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A user stream wrapper passed to ftp_get(), ftp_put(), ftp_append() or the ftp_nb_* variants can call ftp_close() from its stream_read or stream_write handler while the engine still holds the freed ftpbuf_t and databuf_t on the C stack, so the transfer resumes on freed memory. Guard each engine transfer with an in_use flag and make ftp_close() throw while it is set. Closes phpGH-22400
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Superseded by the upstream PR php#22400. |
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ftp_get(),ftp_put(),ftp_append()and theftp_nb_*variants cache theftpbuf_ton the C stack and stream the received or sent bytes through a caller-suppliedphp_stream. When that stream is a user-registered wrapper, itsstream_read/stream_writehandler can callftp_close()on the same connection mid-transfer, freeing the ftpbuf_t anddatabuf_twhile the engine still holds them, so the transfer resumes on freed memory. Valgrind confirms invalid reads in the ftp_get() receive loop, freed by the re-entrant ftp_close(). The fix sets anin_useflag around each engine transfer (includingftp_nb_continue_read/ftp_nb_continue_write, which the non-blocking entry points run through) and makes ftp_close() throw while it is set. Smallest trigger: a wrapper whose stream_write callsftp_close($conn)duringftp_get($conn, 'wrapper://x', ...). Reported privately as GHSA-vr2x-x6ff-4586 and rejected per the project security policy (the trigger is PHP code, not the FTP server), so filing as a normal bug.