From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH] device_cgroup: fix RCU imbalance in error case Date: Tue, 19 Mar 2019 09:33:16 +0100 Message-ID: <20190319083316.GQ8924@dhcp22.suse.cz> References: <20190319013659.86199-1-jannh@google.com> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20190319013659.86199-1-jannh@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jann Horn Cc: James Morris , "Serge E. Hallyn" , Tejun Heo , Li Zefan , Johannes Weiner , linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Aristeu Rozanski , "Serge E . Hallyn" , cgroups@vger.kernel.org On Tue 19-03-19 02:36:59, Jann Horn wrote: > When dev_exception_add() returns an error (due to a failed memory > allocation), make sure that we move the RCU preemption count back to where > it was before we were called. We dropped the RCU read lock inside the loop > body, so we can't just "break". > > sparse complains about this, too: > > $ make -s C=2 security/device_cgroup.o > ./include/linux/rcupdate.h:647:9: warning: context imbalance in > 'propagate_exception' - unexpected unlock > > Fixes: d591fb56618f ("device_cgroup: simplify cgroup tree walk in propagate_exception()") > Cc: stable@vger.kernel.org > Signed-off-by: Jann Horn FWIW looks good to me. Acked-by: Michal Hocko Thanks > --- > Compile-tested only. > > I'm not entirely sure who's supposed to be the maintainer for this thing. > The sign-offs on the commits to this file come from Tejun, but MAINTAINERS > claims it's part of security/, so I'm just sending this to both the > security folks and the cgroup folks, you can figure out whose tree you want > to take this through. :P > If the cgroup folks feel responsible for this file, maybe you could fix up > MAINTAINERS? > > security/device_cgroup.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/security/device_cgroup.c b/security/device_cgroup.c > index cd97929fac66..dc28914fa72e 100644 > --- a/security/device_cgroup.c > +++ b/security/device_cgroup.c > @@ -560,7 +560,7 @@ static int propagate_exception(struct dev_cgroup *devcg_root, > devcg->behavior == DEVCG_DEFAULT_ALLOW) { > rc = dev_exception_add(devcg, ex); > if (rc) > - break; > + return rc; > } else { > /* > * in the other possible cases: > -- > 2.21.0.225.g810b269d1ac-goog -- Michal Hocko SUSE Labs