We already have a small regression test for #15226 within the swraid
installer test. Unfortunately, we only check there whether the md
kthread got signalled but not whether other rampaging processes are
still alive that *should* have been killed.
So in order to do this we provide multiple canary processes which are
checked after the system has booted up:
* canary1: It's a simple forking daemon which just sleeps until it's
going to be killed. Of course we expect this process to not
be alive anymore after boot up.
* canary2: Similar to canary1, but tries to mimick a kthread to make
sure that it's going to be properly killed at the end of
stage 1.
* canary3: Like canary2, but this time using a @ in front of its
command name to actually prevent it from being killed.
* kcanary: This one is a real kthread and it runs until killed, which
shouldn't be the case.
Tested with and without 67223ee and everything works as expected, at
least on my machine.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This is a regression test for #15226, so that the test will fail once we
accidentally kill one or more of the md kthreads (aka: if safe mode is
enabled).
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Unfortunately, pkill doesn't distinguish between kernel and user space
processes, so we need to make sure we don't accidentally kill kernel
threads.
Normally, a kernel thread ignores all signals, but there are a few that
do. A quick grep on the kernel source tree (as of kernel 4.6.0) shows
the following source files which use allow_signal():
drivers/isdn/mISDN/l1oip_core.c
drivers/md/md.c
drivers/misc/mic/cosm/cosm_scif_server.c
drivers/misc/mic/cosm_client/cosm_scif_client.c
drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
drivers/staging/rtl8188eu/core/rtw_cmd.c
drivers/staging/rtl8712/rtl8712_cmd.c
drivers/target/iscsi/iscsi_target.c
drivers/target/iscsi/iscsi_target_login.c
drivers/target/iscsi/iscsi_target_nego.c
drivers/usb/atm/usbatm.c
drivers/usb/gadget/function/f_mass_storage.c
fs/jffs2/background.c
fs/lockd/clntlock.c
fs/lockd/svc.c
fs/nfs/nfs4state.c
fs/nfsd/nfssvc.c
While not all of these are necessarily kthreads and some functionality
may still be unimpeded, it's still quite harmful and can cause
unexpected side-effects, especially because some of these kthreads are
storage-related (which we obviously don't want to kill during bootup).
During discussion at #15226, @dezgeg suggested the following
implementation:
for pid in $(pgrep -v -f '@'); do
if [ "$(cat /proc/$pid/cmdline)" != "" ]; then
kill -9 "$pid"
fi
done
This has a few downsides:
* User space processes which use an empty string in their command line
won't be killed.
* It results in errors during bootup because some shell-related
processes are already terminated (maybe it's pgrep itself, haven't
checked).
* The @ is searched within the full command line, not just at the
beginning of the string. Of course, we already had this until now, so
it's not a problem of his implementation.
I posted an alternative implementation which doesn't suffer from the
first point, but even that one wasn't sufficient:
for pid in $(pgrep -v -f '^@'); do
readlink "/proc/$pid/exe" &> /dev/null || continue
echo "$pid"
done | xargs kill -9
This one spawns a subshell, which would be included in the processes to
kill and actually kills itself during the process.
So what we have now is even checking whether the shell process itself is
in the list to kill and avoids killing it just to be sure.
Also, we don't spawn a subshell anymore and use /proc/$pid/exe to
distinguish between user space and kernel processes like in the comments
of the following StackOverflow answer:
http://stackoverflow.com/a/12231039
We don't need to take care of terminating processes, because what we
actually want IS to terminate the processes.
The only point where this (and any previous) approach falls short if we
have processes that act like fork bombs, because they might spawn
additional processes between the pgrep and the killing. We can only
address this with process/control groups and this still won't save us
because the root user can escape from that as well.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Fixes: #15226
It wants it to detect if there are filesystems present in block devices, in
case of pvcreate. Otherwise it complaints "lvm built without blkid support" and
lacks the feature of detecting/wiping.
Instead of using this option, please modify the dovecot package by means of an
override. For example:
nixpkgs.config.packageOverrides = super: {
dovecot = super.dovecot.override { withPgSQL = true; };
};
Closes https://github.com/NixOS/nixpkgs/issues/14097.
