• Marek Vavruša's avatar
    daemon/worker: fixes error handling from TLS writes · f52231b6
    Marek Vavruša authored
    The error handling loop for uncorking TLS data was wrong, as the
    underlying push function is asynchronous and there's no relationship
    between completed DNS packet writes and number of TLS message writes.
    In case of the asynchronous function, the buffered data must be valid
    until the write is complete, currently this is not guaranteed and
    loading the resolver with pipelined requests results in memory errors:
    
    ```
    $ getdns_query @127.0.0.1#853 -s -a -s -l L -B -F queries -q
    ...
    ==47111==ERROR: AddressSanitizer: heap-use-after-free on address 0x6290040a1253 at pc 0x00010da960d3 bp 0x7ffee2628b30 sp 0x7ffee26282e0
    READ of size 499 at 0x6290040a1253 thread T0
        #0 0x10da960d2 in wrap_write (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x1f0d2)
        #1 0x10d855971 in uv__write (libuv.1.dylib:x86_64+0xf971)
        #2 0x10d85422e in uv__stream_io (libuv.1.dylib:x86_64+0xe22e)
        #3 0x10d85b35a in uv__io_poll (libuv.1.dylib:x86_64+0x1535a)
        #4 0x10d84c644 in uv_run (libuv.1.dylib:x86_64+0x6644)
        #5 0x10d602ddf in main main.c:422
        #6 0x7fff6a28a014 in start (libdyld.dylib:x86_64+0x1014)
    
    0x6290040a1253 is located 83 bytes inside of 16895-byte region [0x6290040a1200,0x6290040a53ff)
    freed by thread T0 here:
        #0 0x10dacdfdd in wrap_free (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x56fdd)
        #1 0x10d913c2e in _mbuffer_head_remove_bytes (libgnutls.30.dylib:x86_64+0xbc2e)
        #2 0x10d915080 in _gnutls_io_write_flush (libgnutls.30.dylib:x86_64+0xd080)
        #3 0x10d90ca18 in _gnutls_send_tlen_int (libgnutls.30.dylib:x86_64+0x4a18)
        #4 0x10d90edde in gnutls_record_send2 (libgnutls.30.dylib:x86_64+0x6dde)
        #5 0x10d90f085 in gnutls_record_uncork (libgnutls.30.dylib:x86_64+0x7085)
        #6 0x10d5f6569 in tls_push tls.c:238
        #7 0x10d5e5b2a in qr_task_send worker.c:1002
        #8 0x10d5e2ea6 in qr_task_finalize worker.c:1562
        #9 0x10d5dab99 in qr_task_step worker.c
        #10 0x10d5e12fe in worker_process_tcp worker.c:2410
    ```
    
    The current implementation adds opportunistic uv_try_write which
    either writes the requested data, or returns UV_EAGAIN or an error,
    which then falls back to slower asynchronous write that copies the buffered data.
    
    The function signature is changed from simple write to vectorized write.
    
    This also enables TLS False Start to save 1RTT when possible.
    f52231b6
bindings.c 43.6 KB