Public bug reported:
DistUpgradeFetcher.py's DistUpgradeFetcher class's gpgauthenticate
method uses the GnuPGInterface.GnuPG to check package signatures. It
requests a stderr handle. Then it reads from the status handle and
waits for the process to exit.
If the gnupg child process writes to stderr, these writes may fill the
stderr buffer (rather easy to do, since stderr is a pipe) and then
block. This will cause the process to never exit and the update-manager
to hang indefinitely.
Another possibility is that the read() call on the status handle will
never return, since the child process will never exit or otherwise close
the status file descriptor, and so the Python read call will wait
indefinitely so that it can return all bytes from the file.
status and stderr should be read from non-blockingly, or an event
notification mechanism (eg select) should be used to read from each
whenever it presents data, and only once each is closed should wait be
called.
** Affects: update-manager (Ubuntu)
Importance: Undecided
Status: Unconfirmed
--
Deadlock opportunity in gpg interaction code
https://launchpad.net/bugs/75832
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