buglwIP - A Lightweight TCP/IP stack - Bugs: bug #57526, Fix the dns entries pcb_idx range


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bug #57526: Fix the dns entries pcb_idx range

Submitted by:  Konstantin <tomcat_84>
Submitted on:  Fri 03 Jan 2020 11:44:52 AM UTC  
Category:  DNS Severity:  3 - Normal
Item Group:  Faulty Behaviour Status:  Invalid
Privacy:  Public Assigned to:  Simon Goldschmidt <goldsimon>
Open/Closed:  Closed Planned Release:  None
lwIP version:  2.1.1

Sat 11 Jan 2020 08:34:55 AM UTC, comment #2: 

Silly me, mixed up the versions.

The behavior was observed in test project, but the version used there was 2.0.0.RC1. :)

A line "entry->state = DNS_STATE_DONE" was missing there, which caused dns_check_entry() to call dns_send() with illegal entry->pcb_idx. This was already fixed in 2.0.0.RC2 .

Sorry for inconvenience.

Best regards,

Konstantin <tomcat_84>
Thu 09 Jan 2020 08:09:02 PM UTC, comment #1: 

I take it this is from reading the code only. Let me explain:
- dns_send() is called for DNS_STATE_NEW and DNS_STATE_ASKING only
- pcb_idx is set to DNS_MAX_SOURCE_PORTS only when the table entry is set to DNS_STATE_UNUSED

Being like that, this cannot happen. I'll add an assert anyway, but no, it currently cannot cause table reading out of range.

Simon Goldschmidt <goldsimon>
Project AdministratorIn charge of this item.
Fri 03 Jan 2020 11:44:52 AM UTC, original submission:  

in dns_send(), when


condition is met, pcb_idx is taken from the dns_table entry.

This pcb_idx probably can be equal to DNS_TABLE_SIZE, being set so elsewhere. It is not tested inside dns_send(). It can cause table reading out of range.

Konstantin <tomcat_84>


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    Follow 3 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2020-01-09 goldsimon StatusNone => Invalid
        Assigned toNone => goldsimon
        Open/ClosedOpen => Closed

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