On Fri, Aug 16, 2019 at 05:19:38PM -0500, Eric W. Biederman wrote: > > My recent to change to only use force_sig for a synchronous events > wound up breaking signal reception cifs and drbd. I had overlooked > the fact that by default kthreads start out with all signals set to > SIG_IGN. So a change I thought was safe turned out to have made it > impossible for those kernel thread to catch their signals. > > Reverting the work on force_sig is a bad idea because what the code > was doing was very much a misuse of force_sig. As the way force_sig > ultimately allowed the signal to happen was to change the signal > handler to SIG_DFL. Which after the first signal will allow userspace > to send signals to these kernel threads. At least for > wake_ack_receiver in drbd that does not appear actively wrong. > > So correct this problem by adding allow_kernel_signal that will allow > signals whose siginfo reports they were sent by the kernel through, > but will not allow userspace generated signals, and update cifs and > drbd to call allow_kernel_signal in an appropriate place so that their > thread can receive this signal. > > Fixing things this way ensures that userspace won't be able to send > signals and cause problems, that it is clear which signals the > threads are expecting to receive, and it guarantees that nothing > else in the system will be affected. > > This change was partly inspired by similar cifs and drbd patches that > added allow_signal. > > Reported-by: ronnie sahlberg <ronniesahlb...@gmail.com> > Reported-by: Christoph Böhmwalder <christoph.boehmwal...@linbit.com> > Cc: Steve French <smfre...@gmail.com> > Cc: Philipp Reisner <philipp.reis...@linbit.com> > Cc: David Laight <david.lai...@aculab.com> > Fixes: 247bc9470b1e ("cifs: fix rmmod regression in cifs.ko caused by > force_sig changes") > Fixes: 72abe3bcf091 ("signal/cifs: Fix cifs_put_tcp_session to call send_sig > instead of force_sig") > Fixes: fee109901f39 ("signal/drbd: Use send_sig not force_sig") > Fixes: 3cf5d076fb4d ("signal: Remove task parameter from force_sig") > Signed-off-by: "Eric W. Biederman" <ebied...@xmission.com> > --- > drivers/block/drbd/drbd_main.c | 2 ++ > fs/cifs/connect.c | 2 +- > include/linux/signal.h | 15 ++++++++++++++- > kernel/signal.c | 5 +++++ > 4 files changed, 22 insertions(+), 2 deletions(-) >
Just tested this patch, and I can confirm that it makes DRBD work as intended again. Tested-by: Christoph Böhmwalder <christoph.boehmwal...@linbit.com> -- Christoph Böhmwalder LINBIT | Keeping the Digital World Running DRBD HA — Disaster Recovery — Software defined Storage