[syslog-ng] [PATCH (3.4)] affile: Fix NULL dereference when opening the destination fails.

[Gergely Nagy]

Gergely Nagy <algernon at balabit.hu> writes:

> Viktor Tusa discovered an error in the affile destination driver: if
> opening the destination failed (for example, due to insufficient
> permissions), next was set to NULL, and later on, at the end of
> affile_dd_open_writer() tried to dereferrence it.
>
> A simple workaround is to return NULL in case next is NULL.
>
> Reported-by: Viktor Tusa <tusa at balabit.hu>
> Signed-off-by: Gergely Nagy <algernon at balabit.hu>

Apparently, this was corrected in 3.3:

commit 33de4c3b4de40493544cee3cf3de8bd0e4d76d34
Author: Balazs Scheidler <bazsi at balabit.hu>
Date:   Sun Jun 12 10:38:18 2011 +0200

    [affile] fixed a reference counting problemin the file-open code

    A reference was leaked whenever the same file got opened from multiple
    threads at about the same time, causing use-after-free problems.

    This patch also fixes a possible NULL deref that could happen if the writer
    couldn't be initialized.

    Signed-off-by: Viktor Juhasz <jviktor at balabit.hu>
    Signed-off-by: Balazs Scheidler <bazsi at balabit.hu>

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