Eric W. Biederman ab7709b551 exec: Transform exec_update_mutex into a rw_semaphore ... [ Upstream commit f7cfd871ae0c5008d94b6f66834e7845caa93c15 ] Recently syzbot reported[0] that there is a deadlock amongst the users of exec_update_mutex. The problematic lock ordering found by lockdep was: perf_event_open (exec_update_mutex -> ovl_i_mutex) chown (ovl_i_mutex -> sb_writes) sendfile (sb_writes -> p->lock) by reading from a proc file and writing to overlayfs proc_pid_syscall (p->lock -> exec_update_mutex) While looking at possible solutions it occured to me that all of the users and possible users involved only wanted to state of the given process to remain the same. They are all readers. The only writer is exec. There is no reason for readers to block on each other. So fix this deadlock by transforming exec_update_mutex into a rw_semaphore named exec_update_lock that only exec takes for writing. Cc: Jann Horn <jannh@google.com> Cc: Vasiliy Kulikov <segoon@openwall.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Bernd Edlinger <bernd.edlinger@hotmail.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Christopher Yeoh <cyeoh@au1.ibm.com> Cc: Cyrill Gorcunov <gorcunov@gmail.com> Cc: Sargun Dhillon <sargun@sargun.me> Cc: Christian Brauner <christian.brauner@ubuntu.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Fixes: eea9673250 ("exec: Add exec_update_mutex to replace cred_guard_mutex") [0] https://lkml.kernel.org/r/00000000000063640c05ade8e3de@google.com Reported-by: syzbot+db9cdf3dd1f64252c6ef@syzkaller.appspotmail.com Link: https://lkml.kernel.org/r/87ft4mbqen.fsf@x220.int.ebiederm.org Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Sasha Levin <sashal@kernel.org>		2021-01-09 13:46:24 +01:00
..
autogroup.h
clock.h
coredump.h	mm, oom_adj: don't loop through tasks in __set_oom_adj when not necessary	2020-10-13 18:38:35 -07:00
cpufreq.h
cputime.h
deadline.h
debug.h	treewide: Convert macro and uses of __section(foo) to __section("foo")	2020-10-25 14:51:49 -07:00
hotplug.h
idle.h
init.h
isolation.h
jobctl.h
loadavg.h
mm.h	mm: kmem: prepare remote memcg charging infra for interrupt contexts	2020-10-18 09:27:09 -07:00
nohz.h
numa_balancing.h
prio.h
rt.h
sd_flags.h
signal.h	exec: Transform exec_update_mutex into a rw_semaphore	2021-01-09 13:46:24 +01:00
smt.h
stat.h
sysctl.h
task_stack.h
task.h
topology.h	sched/topology: Move SD_DEGENERATE_GROUPS_MASK out of linux/sched/topology.h	2020-08-26 12:41:59 +02:00
types.h
user.h
wake_q.h
xacct.h