Re: [net-snmp:patches] #1388 patch for bug 2923: snmpv3 bulkget errors result in double free core dump

On 5/14/19 4:01 PM, Bill Fenner wrote:
> Perhaps getbulk no longer dumps core, but I can not get it to return
> anything but GENERR any more, and, it seems to leak memory.
>
> Any "large enough" request seems to fail in this way, e.g.,
> snmpbulkget -v 3 ... -Cn 5 -Cr 50 sysUpTime sysUpTime sysUpTime
> sysUpTime sysUpTime .1
>
> This is particularly frustrating because code was added to 5.8 to
> rebuild a getbulk reply if it's too big.  But there was already code
> to not build the PDU too big, it's just not taking the v3 header into
> account properly (that's my best guess, at least).  So now there are
> two different mechanisms to send a "right-size" reply and they both
> don't work.  Around 5.8 release time I was working with Robert Story
> to fix this, but that effort kind of petered out and Robert's work
> didn't make it into git.
>
> Can anyone get getbulk to work in the current 5.8-patches with SNMPv3?
>
> I've attached a test script with 504 failing test cases when I run it
> against an unmodified V5-8-patches branch, and net-snmp leaks about a
> meg of RAM during the test.  This is an adaptation of my internal test
> to the net-snmp test framework; the complete test would use all
> supported values for -l, -a, -x but for now this is the simplest one
> using nanp.


Hi Bill,

A new test has been added
(testing/fulltests/default/T0221snmpbulkget_large_simple). That test
passes on my setup. Can you have a look whether that test covers the
issue you ran into?

Regarding the "memory leak": RSS is not a reliable source of information
to detect memory leaks. If you want to verify whether or not a new
memory leak has been introduced please use Valgrind.

Bart.




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