Re: [PATCH] channels: Fix segfaults when the channel data is freed
- Subject: Re: [PATCH] channels: Fix segfaults when the channel data is freed
- From: Jakub Jelen <jjelen@xxxxxxxxxx>
- Reply-to: libssh@xxxxxxxxxx
- Date: Mon, 16 Aug 2021 12:40:52 +0200
- To: libssh@xxxxxxxxxx
On 8/15/21 10:01 PM, Artyom V. Poptsov wrote:
I've found that some channel procedures in libssh 0.9.3 on Ubuntu
GNU/Linux 20.04 (and the latest versions from Git) fails with SEGFAULT
when a parent session of a channel is freed.
I investigated the errors and found that some "channels.h" procedures
(namely 'ssh_channel_is_open' and 'ssh_channel_is_closed') try to
determine whether the parent session is alive by checking
'channel->session->alive' variable. But when a channel is freed by
'ssh_channel_do_free' procedure, its 'session' field is set to NULL. In
that situation calling e.g. 'ssh_channel_is_open' on a channel will lead
to a SEGFAULT.
The patch to fix that behavior is attached to the email.
I ran "make test" on the libssh sources with my changes and all tests
have passed successfully.
Thank you for the patch!
It looks fine to me technically, but can you adjust the formatting to
match the coding style? Mostly minor details as spaces after "if" and
aligning opening braces of multiline conditions (with moving the && to
the end of previous lines) and replacing "! channel->session" with
explicit check for NULL.
Do you have a simple way how to reproduce the behavior you encountered
inside of the testsuite to make sure we will not reintroduce the issue
in the future?
You can also submit a merge request in gitlab, which will run all testes
on different configurations:
Crypto Team, Security Engineering
Red Hat, Inc.
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