Another curl scan shows work to do

Friday, October 10th, 2008

The nice guys on Coverity did a new scan on curl (the 7.19.0 source code) and they dug a bunch of new flaws. The previous version they checked was 7.16.1, release some 20 months before. The new changes are not only because of how the code has changed in the mean time, but it seems their scanner have improved a bit since the last time as well!

Here’s a sample view of how libcurl might dereference a NULL pointer with a step-by-step explanation on what conditions that lead to the flaw:

They identify 22 flaws and I found it interesting to compare the top list of bad functions as reported by Coverity with the complexity list I showed the other day. First we need to ignore the 9 flaws Coverity found in the ‘curl’ tool code (i.e not within the library). Then the 10 remaining functions with flaws marked by Coverity are:

  • Curl_getinfo (4 flaws, all the other ones have one each)
  • Curl_cookie_add (present in the complexity top-10 table)
  • FormAdd (present in the complexity top-10 table)
  • parsedate
  • ftp_parse_url_path
  • tftp_do
  • resolve_server
  • curl_easy_pause
  • add_closure
  • Curl_connect

See? Only two of them were present in that list. The Coverity tool does in fact also count the complexity for each function, and while it doesn’t match the values pmccabe shows exactly, they seem to agree in general about what functions that are the most complex ones.

Ok, now let’s go work on fixing all these problems…

Posted in cURL and libcurl | Comments Off

Coverity’s open source bug report

Tuesday, May 20th, 2008

The great guys at scan.coverity.com published their Open Source Report 2008 in which they detail findings about source code they’ve monitored and how quality and bug density etc have changed over time since they started scanning over 250 popular open source projects. curl is one of the projects included.

Some highlights from the report:

  • curl is mentioned as one of the (few) projects that fixed all defects identified by coverity
  • from their start, the average defect frequency has gone down from one defect per 3333 lines of code to one defect per 4000 lines
  • they find no support to backup the old belief that there’s a correlation between function length and bug count
  • the average function length is 66 lines

And the top-5 most frequently detected defects are:

  1. NULL Pointer Dereference 28%
  2. Resource Leak 26%
  3. Unintentional Ignored Expressions 10%
  4. Use Before Test (NULL) 8%
  5. Buffer Overrun (statically allocated) 6%

For all details and more fun reading, see the full Open Source Report 2008 (1MB pdf)

Posted in Development, Open Source, Security | Comments Off