Upstream bug management in Linux distributionsAn empirical study of Debian and Fedora practices

A Linux distribution consists of thousands of packages that are either developed by in-house developers (in-house packages) or by external projects (upstream packages). Leveraging upstream packages speeds up development and improves productivity, yet bugs might slip through into the packaged code and end up propagating into downstream Linux distributions. Maintainers, who integrate upstream projects into their distribution, typically lack the expertise of the upstream projects. Hence, they could try either to propagate the bug report upstream and wait for a fix, or fix the bug locally and maintain the fix until it is incorporated upstream. Both of these outcomes come at a cost, yet, to the best of our knowledge, no prior work has conducted an in-depth analysis of upstream bug management in the Linux ecosystem. Hence, this paper empirically studies how high-severity bugs are fixed in upstream packages for two Linux distributions, i.e., Debian and Fedora. Our results show that 13.9% of the upstream package bugs are explicitly reported being fixed by upstream, and 13.3% being fixed by the distribution, while the vast majority of bugs do not have explicit information about this in Debian. When focusing on the 27.2% with explicit information, our results also indicate that upstream fixed bugs make users wait for a longer time to get fixes and require more additional information compared to fixing upstream bugs locally by the distribution. Finally, we observe that the number of bug comment links to reference information (e.g., design docs, bug reports) of the distribution itself and the similarity score between upstream and distribution bug reports are important factors for the likelihood of a bug being fixed upstream. Our findings strengthen the need for traceability tools on bug fixes of upstream packages between upstream and distributions in order to find upstream fixes easier and lower the cost of upstream bug management locally.