[Dovecot] File descriptor leak in sieve-extprograms

[Stephan Bosch]

On 12/13/2013 2:07 AM, Kirill A. Shutemov wrote:
> I've tried to use sieve-filter for my inbox (~6000 messages). It failed after
> some work with this backtrace:
>
> sieve-filter(kas): Error: socketpair() failed: Too many open files
> sieve-filter(kas): Panic: file script-client-local.c: line 155 (script_client_local_disconnect): assertion failed: (pid >= 0)
> sieve-filter(kas): Error: Raw backtrace: /usr/lib/dovecot/libdovecot.so.0(+0x66a71) [0x7f020e717a71] -> /usr/lib/dovecot/libdovecot.so.0(default_fatal_handler+0x2a) [0x7f020e717ada] -> /usr/lib/dovecot/libdovecot.so.0(i_fatal+0) [0x7f020e6d32ee] -> /usr/lib/dovecot/modules/sieve/lib90_sieve_extprograms_plugin.so(+0x4baf) [0x7f020dae0baf] -> /usr/lib/dovecot/modules/sieve/lib90_sieve_extprograms_plugin.so(+0x58ca) [0x7f020dae18ca] -> /usr/lib/dovecot/modules/sieve/lib90_sieve_extprograms_plugin.so(script_client_fail+0x2f) [0x7f020dae199f] -> /usr/lib/dovecot/modules/sieve/lib90_sieve_extprograms_plugin.so(script_client_run+0xc4) [0x7f020dae1fd4] -> /usr/lib/dovecot/modules/sieve/lib90_sieve_extprograms_plugin.so(+0x6134) [0x7f020dae2134] -> /usr/lib/dovecot/libdovecot-sieve.so.0(sieve_result_execute+0x3ac) [0x7f020ecd1adc] -> /usr/lib/dovecot/libdovecot-sieve.so.0(sieve_execute+0x4a) [0x7f020ece05aa] -> /usr/bin/sieve-filter(main+0x6a9) [0x403b49] -> /usr/lib/libc.so.6(__libc_
>  start_ma
>  in+0xf5) [0x7f020e327bc5] -> /usr/bin/sieve-filter() [0x404111]
>
> The reason is file descriptor leak in "script client local".
> script_client_local_close_output() shutdowns write side of descriptor
> and sets sclient->fd_out to -1, but never closes the descriptor.
>
> I've tried to fix this by the patch below. Tests works fine, but sieve-filter
> crashed in other way:

Wow, this is a very interesting stupidity on my part, especially the
`sclient->fd_out != sclient->fd_out`.

This probably fixes it, although I am not entirely sure. I am mainly a
bit puzzled on how this causes the fd leak; the fd_in and fd_out are for
the current backends always the same fd.

Regards,

Stephan.