Eric W. Biederman b796d94921 exec: Add exec_update_mutex to replace cred_guard_mutex ... [ Upstream commit eea9673250 ] The cred_guard_mutex is problematic as it is held over possibly indefinite waits for userspace. The possible indefinite waits for userspace that I have identified are: The cred_guard_mutex is held in PTRACE_EVENT_EXIT waiting for the tracer. The cred_guard_mutex is held over "put_user(0, tsk->clear_child_tid)" in exit_mm(). The cred_guard_mutex is held over "get_user(futex_offset, ...") in exit_robust_list. The cred_guard_mutex held over copy_strings. The functions get_user and put_user can trigger a page fault which can potentially wait indefinitely in the case of userfaultfd or if userspace implements part of the page fault path. In any of those cases the userspace process that the kernel is waiting for might make a different system call that winds up taking the cred_guard_mutex and result in deadlock. Holding a mutex over any of those possibly indefinite waits for userspace does not appear necessary. Add exec_update_mutex that will just cover updating the process during exec where the permissions and the objects pointed to by the task struct may be out of sync. The plan is to switch the users of cred_guard_mutex to exec_update_mutex one by one. This lets us move forward while still being careful and not introducing any regressions. Link: https://lore.kernel.org/lkml/20160921152946.GA24210@dhcp22.suse.cz/ Link: https://lore.kernel.org/lkml/AM6PR03MB5170B06F3A2B75EFB98D071AE4E60@AM6PR03MB5170.eurprd03.prod.outlook.com/ Link: https://lore.kernel.org/linux-fsdevel/20161102181806.GB1112@redhat.com/ Link: https://lore.kernel.org/lkml/20160923095031.GA14923@redhat.com/ Link: https://lore.kernel.org/lkml/20170213141452.GA30203@redhat.com/ Ref: 45c1a159b85b ("Add PTRACE_O_TRACEVFORKDONE and PTRACE_O_TRACEEXIT facilities.") Ref: 456f17cd1a28 ("[PATCH] user-vm-unlock-2.5.31-A2") Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Sasha Levin <sashal@kernel.org>		2020-10-01 13:17:47 +02:00
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autogroup.h	…
clock.h	…
coredump.h	…
cpufreq.h	cpufreq: Avoid leaving stale IRQ work items during CPU offline	2019-12-31 16:46:06 +01:00
cputime.h	posix-cpu-timers: Move state tracking to struct posix_cputimers	2019-08-28 11:50:42 +02:00
deadline.h	cpusets: Rebuild root domain deadline accounting information	2019-07-25 15:55:01 +02:00
debug.h	…
hotplug.h	…
idle.h	…
init.h	…
isolation.h	KVM: LAPIC: Inject timer interrupt via posted interrupt	2019-07-20 09:00:40 +02:00
jobctl.h	cgroup: cgroup v2 freezer	2019-04-19 11:26:48 -07:00
loadavg.h	…
mm.h	sched/core: Fix illegal RCU from offline CPUs	2020-06-22 09:31:01 +02:00
nohz.h	timers/nohz: Update NOHZ load in remote tick	2020-03-05 16:43:36 +01:00
numa_balancing.h	sched/fair: Don't free p->numa_faults with concurrent readers	2019-07-25 15:37:04 +02:00
prio.h	…
rt.h	…
signal.h	exec: Add exec_update_mutex to replace cred_guard_mutex	2020-10-01 13:17:47 +02:00
smt.h	…
stat.h	…
sysctl.h	sched/uclamp: Add system default clamps	2019-06-24 19:23:45 +02:00
task.h	tasks, sched/core: With a grace period after finish_task_switch(), remove unnecessary code	2019-09-25 17:42:29 +02:00
task_stack.h	…
topology.h	sched/topology: Add partition_sched_domains_locked()	2019-07-25 15:51:57 +02:00
types.h	posix-cpu-timers: Provide array based access to expiry cache	2019-08-28 11:50:35 +02:00
user.h	keys: Move the user and user-session keyrings to the user_namespace	2019-06-26 21:02:32 +01:00
wake_q.h	locking/rwsem: Always release wait_lock before waking up tasks	2019-06-17 12:28:00 +02:00
xacct.h	…