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Sometimes it may be necessary to send empty STREAM frames with only the FIN bit set. For these frames, memcpy is thus unnecessary as their payload is empty. However, we did not prevent its invocation inside quic_build_stream_frame(). Normally, memcpy invocation with length==0 is safe. However, there is an extra condition in our function to handle data wrapping. For an empty STREAM frame in the context of MUX emission, this is safe as the frame points to a valid buffer which causes the wrapping condition to be false and resulting in a memcpy with 0 length. However, in the context of retransmission, this may lead to a crash. Consider the following scenario : two STREAM frames A and B are produced, one with payload and one empty with FIN set, pointing to the same stream_desc buffer. If A is acknowledged by the peer, its buffer is released as no more data is left in it. If B needs to be resent, the wrapping condition will be messed up to a reuse of a freed buffer. Most of the times, <wrap> will be a negative number, which results in a memcpy invocation causing a buffer overflow. To fix this, simply add an extra condition to skip memcpy and wrapping check if STREAM frame length is null inside quic_build_stream_frame(). This crash is pretty rare as it relies on a lot of conditions difficult to reproduce. It seems to be the cause for the latest crashes reported under github issue #2120. In all the inspected dumps, the segfault occurred during retransmission with an empty STREAM frame being used as input. Thanks again to Tristan from Mangadex for his help and investigation on it. This should be backported up to 2.6.
The HAProxy documentation has been split into a number of different files for ease of use. Please refer to the following files depending on what you're looking for : - INSTALL for instructions on how to build and install HAProxy - BRANCHES to understand the project's life cycle and what version to use - LICENSE for the project's license - CONTRIBUTING for the process to follow to submit contributions The more detailed documentation is located into the doc/ directory : - doc/intro.txt for a quick introduction on HAProxy - doc/configuration.txt for the configuration's reference manual - doc/lua.txt for the Lua's reference manual - doc/SPOE.txt for how to use the SPOE engine - doc/network-namespaces.txt for how to use network namespaces under Linux - doc/management.txt for the management guide - doc/regression-testing.txt for how to use the regression testing suite - doc/peers.txt for the peers protocol reference - doc/coding-style.txt for how to adopt HAProxy's coding style - doc/internals for developer-specific documentation (not all up to date)