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Cisco Bug: CSCun71762 - 100-Continue handshake causes KDB

Last Modified

Jun 21, 2020

Products (4)

  • Cisco Videoscape Distribution Suite for Television
  • Cisco TV Streamer Application
  • Cisco Visual Quality Experience (VQE) Channel Provisioning Tools
  • Cisco Visual Quality Experience Application

Known Affected Releases

1.0(0) 3.4(2)

Description (partial)

Symptom:
Recorder crashes when archiving recorded content, and either reboots with a core file generated, or traps into kernel debugger.

Conditions:
The recorder uses an HTTP PUT verb to initiate sending data to an archive.  The HTTP PUT semantics allows for the client (recorder) to send an "Expect: 100-Continue" header as part of the initial HTTP PUT send by the recorder to server (archive).  When using the 100-Continue handshake, the recorder will then wait to start sending the data for the PUT until the archive sends back a 100-Continue message.  This 100-Continue handshake gives the archive an opportunity to reject the PUT request before the client starts blasting data.

Without using the 100-Continue handshake, the recorder will just start blasting data to the archive immediately after sending the initial HTTP PUT.  The 100-Continue handshake is new code in the 3.4.2 branch.  This new code has a window of opportunity where if the 100-Continue response from the archive shows up is close proximity of time to a 10 second timeout after having sent the PUT request, the recorder can attempt to dereference a NULL pointer.
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