Resolve issue #832 (Potential memory corruption) #835
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The memmove command is executed without any sanity checking on used values causing random reboots when an MQTT package gets processed with an impossible topic length. With a high rate test flow of MQTT messages this would sometimes corrupt memory after a few seconds. Extra sanity checks and calculation for payload_offset and message length have been implemented to better handle messages and prevent this memory corruption. Tested with a flow of about 50.000 messages per hour for multiple days. Went from hunderds of errors per hour til a few per day, the last errors mainly because the MQTT server couldn't keep up with the message flow. Never crashed again.
TD-er
reviewed
Feb 27, 2021
| @@ -368,7 +368,7 @@ uint32_t PubSubClient::readPacket(uint8_t* lengthLength) { | |||
| } | |||
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| boolean PubSubClient::loop_read() { | |||
| if (_client == nullptr) { | |||
| if (_client == NULL) { | |||
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Why do this change?
NULL is not a pointer type, so the compiler cannot help you here to check for wrong usage.
nullptr is a pointer type, so it is an improvement over the old NULL
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Just because otherwise the travis ci build behind the repo doesn't run
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Hmm that's strange.
What kind of compiler or compiler settings is used?
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if you click on 'details' behind "continuous-integration/travis-ci/pr — The Travis CI build failed"
you see all the build system info
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Any update on this PR? It it going to get merged? |
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The memmove command is executed without any sanity checking on used values causing random reboots when an MQTT package gets processed with an impossible topic length.
With a high rate test flow of MQTT messages this would sometimes corrupt memory after a few seconds.
Extra sanity checks and calculation for payload_offset and message length have been implemented to better handle messages and prevent this memory corruption.
Tested with a flow of about 50.000 messages per hour for multiple days. Went from hundreds of errors per hour to a few per day, the last errors mainly because the MQTT server couldn't keep up with the message flow. Never crashed again.
A big thanks to @TD-er for help with further refactoring the code.