Messages in this thread | | | Date | Wed, 29 Jan 2020 14:12:03 -0500 | From | Sasha Levin <> | Subject | Re: [PATCH 4.9 183/271] signal: Allow cifs and drbd to receive their terminating signals |
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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@xmission.com> >> > >> > [ 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@gmail.com> >> > Reported-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com> >> > Tested-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com> >> > Cc: Steve French <smfrench@gmail.com> >> > Cc: Philipp Reisner <philipp.reisner@linbit.com> >> > Cc: David Laight <David.Laight@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") >> >> 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
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