[tor-bugs] #9980 [Tor]: (cp >= end) in channel_tls_process_netinfo_cell confuses analysis tools

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#9980: (cp >= end) in channel_tls_process_netinfo_cell confuses analysis tools
------------------------+------------------------------------
 Reporter:  nickm       |          Owner:
     Type:  defect      |         Status:  new
 Priority:  normal      |      Milestone:  Tor: 0.2.5.x-final
Component:  Tor         |        Version:
 Keywords:  tor-client  |  Actual Points:
Parent ID:              |         Points:
------------------------+------------------------------------
 David Fifield reports that:
 {{{
   my_addr_len = (uint8_t) cell->payload[5];
   end = cell->payload + CELL_PAYLOAD_SIZE;
   cp = cell->payload + 6 + my_addr_len;
   if (cp >= end) {
     ...
     return;
   }
 }}}
 confuses the STACK analysis tool because the check could get optimized
 away.  This check is indeed needless, since CELL_PAYLOAD_SIZE is 509, but
 UINT8_MAX + 6 is only 261, so that branch can never be taken.  Shall we
 just remove it?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/9980>
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