Bug#795934: evince: doesn't close network connections after opening documents from thunderbird/icedove

[Simon McVittie]

Control: reassign 795934 icedove
Control: retitle 795934 leaks file descriptors to attachment handlers
Control: found 795934 38.1.0-1

On 18/08/15 08:12, Andrew King wrote:
> After opening pdf attachments from my mail client (icedove), each
> evince process keeps an open network connection to the mail server (long
> after the document has completed loading).
> 
> (I'm assuming that evince is retrieving the document, otherwise I am
> unsure why it needs a network connection in the first place).

evince does not retrieve the document itself; icedove does give it a
filename in /tmp for the attachment.

The problem is that evince is executed as a subprocess of icedove, and
icedove does not either mark its open file descriptors as close-on-exec,
or close all file descriptors (except for stdin, stdout, stderr and any
other deliberately-inherited fds) in the child process after fork() but
before exec(). Any process that executes subprocesses should do at least
one of those two things, preferably both.

As a result, file descriptors that were open in icedove (including
sockets, pipes, the cache, and mailbox files) remain open in the child
process.

I can reproduce this with a different attachment handler, which
demonstrates that this is not unique to evince: if I open an attachment
with gvim, then "ls -l /proc/$(pgrep gvim)/fd", I can see that gvim has
incorrectly inherited various open file descriptors pointing to sockets,
pipes, ~/.icedove/*/Cache/*, and ~/.icedove/*/ImapMail/*/*.msf.

Quoting the rest of Andrew's report for the icedove maintainer.

> The problem is that after I have 10 documents open my mail client is
> unable to contact (or authenticate to) the mail server as it limits the
> number of active connections to 10 per IP.
> 
> Evince should close the connection once the document is loaded, or
> better yet, load the document from /tmp and not make/keep any network
> connections.
> 
> The immediate workaround is to save all attachments and then open
> them (which is somewhat inconvenient).

Regards,
    S