[PATCH] Set PR_SET_DUMPABLE before switching uid to allow core dumps.

[Ondrej Zajicek]

On Fri, Jan 13, 2023 at 03:21:36PM +0100, Thomas Liske wrote:
> Signed-off-by: Thomas Liske <liske at ibh.de>
> ---
> 
> This patch sets the PR_SET_DUMPABLE capability before switching
> to a unprivileged user to allow core dumps (see also the paragraph
> about set-user-ID in `man 5 core`)
> 
> Background: While debugging bird on Alpine we wonder why it was
> not possible to get a core dump when bird runs under a unprivileged
> user.

Hi

Sorry for later reply. Did not know about this issue with core dumps. It
is interesting nobody noticed that before. I am not really sure why using
setresuid() has the same core dump restriction as set-user-ID programs,
considering it changes both real and effective UID.

Using prctl(PR_SET_DUMPABLE) has some strange side-effects in changing
ownership of /proc/<pid>/* fields. Not really sure what are implications
of that.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
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"To err is human -- to blame it on a computer is even more so."