On Wed, Jan 29, 2020 at 12:36:43PM +0100, Greg Kroah-Hartman wrote:
On Wed, Jan 29, 2020 at 12:10:47PM +0100, Thomas Voegtle wrote:On Tue, 28 Jan 2020, Greg Kroah-Hartman wrote: > From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> > > [ Upstream commit 33da8e7c814f77310250bb54a9db36a44c5de784 ] > > 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 <ronniesahlberg@xxxxxxxxx> > Reported-by: Christoph Böhmwalder <christoph.boehmwalder@xxxxxxxxxx> > Tested-by: Christoph Böhmwalder <christoph.boehmwalder@xxxxxxxxxx> > Cc: Steve French <smfrench@xxxxxxxxx> > Cc: Philipp Reisner <philipp.reisner@xxxxxxxxxx> > Cc: David Laight <David.Laight@xxxxxxxxxx> > 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") These two commits come with that release, but... > Fixes: fee109901f39 ("signal/drbd: Use send_sig not force_sig") > Fixes: 3cf5d076fb4d ("signal: Remove task parameter from force_sig") ...these two commits not and were never added to 4.9.y. Are these both really not needed?I don't think so, do you feel otherwise?
Both of those commits read as a cleanup to me. I've actually slightly modified to patch to not need those commits (they were less than trivial to backport as is). -- Thanks, Sasha
