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Luis Chamberlain 3740d93e37 coredump: fix crash when umh is disabled 
Commit 64e90a8acb859 ("Introduce STATIC_USERMODEHELPER to mediate
call_usermodehelper()") added the optiont to disable all
call_usermodehelper() calls by setting STATIC_USERMODEHELPER_PATH to
an empty string. When this is done, and crashdump is triggered, it
will crash on null pointer dereference, since we make assumptions
over what call_usermodehelper_exec() did.

This has been reported by Sergey when one triggers a a coredump
with the following configuration:

```
CONFIG_STATIC_USERMODEHELPER=y
CONFIG_STATIC_USERMODEHELPER_PATH=""
kernel.core_pattern = |/usr/lib/systemd/systemd-coredump %P %u %g %s %t %c %h %e
```

The way disabling the umh was designed was that call_usermodehelper_exec()
would just return early, without an error. But coredump assumes
certain variables are set up for us when this happens, and calls
ile_start_write(cprm.file) with a NULL file.

[    2.819676] BUG: kernel NULL pointer dereference, address: 0000000000000020
[    2.819859] #PF: supervisor read access in kernel mode
[    2.820035] #PF: error_code(0x0000) - not-present page
[    2.820188] PGD 0 P4D 0
[    2.820305] Oops: 0000 [#1] SMP PTI
[    2.820436] CPU: 2 PID: 89 Comm: a Not tainted 5.7.0-rc1+ #7
[    2.820680] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190711_202441-buildvm-armv7-10.arm.fedoraproject.org-2.fc31 04/01/2014
[    2.821150] RIP: 0010:do_coredump+0xd80/0x1060
[    2.821385] Code: e8 95 11 ed ff 48 c7 c6 cc a7 b4 81 48 8d bd 28 ff
ff ff 89 c2 e8 70 f1 ff ff 41 89 c2 85 c0 0f 84 72 f7 ff ff e9 b4 fe ff
ff <48> 8b 57 20 0f b7 02 66 25 00 f0 66 3d 00 8
0 0f 84 9c 01 00 00 44
[    2.822014] RSP: 0000:ffffc9000029bcb8 EFLAGS: 00010246
[    2.822339] RAX: 0000000000000000 RBX: ffff88803f860000 RCX: 000000000000000a
[    2.822746] RDX: 0000000000000009 RSI: 0000000000000282 RDI: 0000000000000000
[    2.823141] RBP: ffffc9000029bde8 R08: 0000000000000000 R09: ffffc9000029bc00
[    2.823508] R10: 0000000000000001 R11: ffff88803dec90be R12: ffffffff81c39da0
[    2.823902] R13: ffff88803de84400 R14: 0000000000000000 R15: 0000000000000000
[    2.824285] FS:  00007fee08183540(0000) GS:ffff88803e480000(0000) knlGS:0000000000000000
[    2.824767] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    2.825111] CR2: 0000000000000020 CR3: 000000003f856005 CR4: 0000000000060ea0
[    2.825479] Call Trace:
[    2.825790]  get_signal+0x11e/0x720
[    2.826087]  do_signal+0x1d/0x670
[    2.826361]  ? force_sig_info_to_task+0xc1/0xf0
[    2.826691]  ? force_sig_fault+0x3c/0x40
[    2.826996]  ? do_trap+0xc9/0x100
[    2.827179]  exit_to_usermode_loop+0x49/0x90
[    2.827359]  prepare_exit_to_usermode+0x77/0xb0
[    2.827559]  ? invalid_op+0xa/0x30
[    2.827747]  ret_from_intr+0x20/0x20
[    2.827921] RIP: 0033:0x55e2c76d2129
[    2.828107] Code: 2d ff ff ff e8 68 ff ff ff 5d c6 05 18 2f 00 00 01
c3 0f 1f 80 00 00 00 00 c3 0f 1f 80 00 00 00 00 e9 7b ff ff ff 55 48 89
e5 <0f> 0b b8 00 00 00 00 5d c3 66 2e 0f 1f 84 0
0 00 00 00 00 0f 1f 40
[    2.828603] RSP: 002b:00007fffeba5e080 EFLAGS: 00010246
[    2.828801] RAX: 000055e2c76d2125 RBX: 0000000000000000 RCX: 00007fee0817c718
[    2.829034] RDX: 00007fffeba5e188 RSI: 00007fffeba5e178 RDI: 0000000000000001
[    2.829257] RBP: 00007fffeba5e080 R08: 0000000000000000 R09: 00007fee08193c00
[    2.829482] R10: 0000000000000009 R11: 0000000000000000 R12: 000055e2c76d2040
[    2.829727] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[    2.829964] CR2: 0000000000000020
[    2.830149] ---[ end trace ceed83d8c68a1bf1 ]---
```

Cc: <stable@vger.kernel.org> # v4.11+
Fixes: 64e90a8acb85 ("Introduce STATIC_USERMODEHELPER to mediate call_usermodehelper()")
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=199795
Reported-by: Tony Vroon <chainsaw@gentoo.org>
Reported-by: Sergey Kvachonok <ravenexp@gmail.com>
Tested-by: Sergei Trofimovich <slyfox@gentoo.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20200416162859.26518-1-mcgrof@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-04-28 17:54:13 +02:00
..
bpf
bpf: Make bpf_link_fops static
2020-04-24 17:42:44 -07:00
cgroup
Merge branch 'for-5.7' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
2020-04-03 11:30:20 -07:00
configs
compiler: remove CONFIG_OPTIMIZE_INLINING entirely
2020-04-07 10:43:42 -07:00
debug
SPDX patches for 5.7-rc1.
2020-04-03 13:12:26 -07:00
dma
dma-debug: fix displaying of dma allocation type
2020-04-08 21:46:57 +02:00
events
perf/core: fix parent pid/tid in task exit events
2020-04-22 23:10:14 +02:00
gcov
kernel/gcov/fs.c: gcov_seq_next() should increase position index
2020-04-10 15:36:22 -07:00
irq
genirq: Remove setup_irq() and remove_irq()
2020-04-14 10:08:50 +02:00
livepatch
New tracing features:
2019-11-27 11:42:01 -08:00
locking
locking/lockdep: Improve 'invalid wait context' splat
2020-04-08 12:05:07 +02:00
power
PM / sleep: handle the compat case in snapshot_set_swap_area()
2020-04-06 21:42:36 +02:00
printk
printk: queue wake_up_klogd irq_work only if per-CPU areas are ready
2020-04-10 13:18:57 -07:00
rcu
Merge branch 'urgent-for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/urgent
2020-04-14 08:36:41 +02:00
sched
sched/core: Fix reset-on-fork from RT with uclamp
2020-04-22 23:10:13 +02:00
time
proc, time/namespace: Show clock symbolic names in /proc/pid/timens_offsets
2020-04-16 12:10:54 +02:00
trace
tracing: Convert local functions in tracing_map.c to static
2020-04-22 22:07:26 -04:00
.gitignore
.gitignore: add SPDX License Identifier
2020-03-25 11:50:48 +01:00
acct.c
acct: stop using get_seconds()
2019-12-18 18:07:31 +01:00
async.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441
2019-06-05 17:37:17 +02:00
audit_fsnotify.c
fsnotify: use helpers to access data by data_type
2020-03-23 18:19:06 +01:00
audit_tree.c
…
audit_watch.c
\n
2020-04-06 08:58:42 -07:00
audit.c
audit: check the length of userspace generated audit records
2020-04-20 17:10:58 -04:00
audit.h
audit: trigger accompanying records when no rules present
2020-03-12 10:42:51 -04:00
auditfilter.c
audit: fix error handling in audit_data_to_entry()
2020-02-22 20:36:47 -05:00
auditsc.c
audit: trigger accompanying records when no rules present
2020-03-12 10:42:51 -04:00
backtracetest.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441
2019-06-05 17:37:17 +02:00
bounds.c
…
capability.c
…
compat.c
y2038: remove unused time32 interfaces
2020-02-21 11:22:15 -08:00
configs.c
proc: convert everything to "struct proc_ops"
2020-02-04 03:05:26 +00:00
context_tracking.c
context-tracking: Introduce CONFIG_HAVE_TIF_NOHZ
2020-02-14 16:05:04 +01:00
cpu_pm.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 282
2019-06-05 17:36:37 +02:00
cpu.c
CPU (hotplug) updates:
2020-03-30 18:06:39 -07:00
crash_core.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 230
2019-06-19 17:09:06 +02:00
crash_dump.c
…
cred.c
kernel: doc: remove outdated comment cred.c
2020-03-25 10:04:01 -05:00
delayacct.c
…
dma.c
…
elfcore.c
kernel/elfcore.c: include proper prototypes
2019-09-25 17:51:39 -07:00
exec_domain.c
…
exit.c
proc: Put thread_pid in release_task not proc_flush_pid
2020-04-24 15:49:00 -05:00
extable.c
kernel/extable.c: use address-of operator on section symbols
2020-04-07 10:43:42 -07:00
fail_function.c
fail_function: no need to check return value of debugfs_create functions
2019-06-03 15:49:06 +02:00
fork.c
clone3: add build-time CLONE_ARGS_SIZE_VER* validity checks
2020-04-15 09:56:32 +02:00
freezer.c
Revert "libata, freezer: avoid block device removal while system is frozen"
2019-10-06 09:11:37 -06:00
futex.c
Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2020-03-30 16:17:15 -07:00
gen_kheaders.sh
kheaders: explain why include/config/autoconf.h is excluded from md5sum
2019-11-11 20:10:01 +09:00
groups.c
…
hung_task.c
…
iomem.c
mm/nvdimm: add is_ioremap_addr and use that to check ioremap address
2019-07-12 11:05:40 -07:00
irq_work.c
lockdep: Annotate irq_work
2020-03-21 16:00:24 +01:00
jump_label.c
jump_label: Don't warn on __exit jump entries
2019-08-29 15:10:10 +01:00
kallsyms.c
kallsyms: unexport kallsyms_lookup_name() and kallsyms_on_each_symbol()
2020-04-07 10:43:44 -07:00
kcmp.c
kernel/kcmp.c: Use new infrastructure to fix deadlocks in execve
2020-03-25 10:04:01 -05:00
Kconfig.freezer
…
Kconfig.hz
…
Kconfig.locks
sched/rt, locking: Use CONFIG_PREEMPTION
2019-12-08 14:37:36 +01:00
Kconfig.preempt
sched/Kconfig: Fix spelling mistake in user-visible help text
2019-11-12 11:35:32 +01:00
kcov.c
kcov: remote coverage support
2019-12-04 19:44:14 -08:00
kexec_core.c
kexec: add machine_kexec_post_load()
2020-01-08 16:32:55 +00:00
kexec_elf.c
kexec_elf: support 32 bit ELF files
2019-09-06 23:58:44 +02:00
kexec_file.c
kexec: add machine_kexec_post_load()
2020-01-08 16:32:55 +00:00
kexec_internal.h
kexec: add machine_kexec_post_load()
2020-01-08 16:32:55 +00:00
kexec.c
kexec: add machine_kexec_post_load()
2020-01-08 16:32:55 +00:00
kheaders.c
…
kmod.c
kmod: make request_module() return an error when autoloading is disabled
2020-04-10 15:36:22 -07:00
kprobes.c
kprobes: Fix optimize_kprobe()/unoptimize_kprobe() cancellation logic
2020-01-09 12:40:13 +01:00
ksysfs.c
…
kthread.c
kthread: Do not preempt current task if it is going to call schedule()
2020-03-20 13:06:20 +01:00
latencytop.c
proc: convert everything to "struct proc_ops"
2020-02-04 03:05:26 +00:00
Makefile
kcov: ignore fault-inject and stacktrace
2020-01-31 10:30:41 -08:00
module_signature.c
MODSIGN: Export module signature definitions
2019-08-05 18:39:56 -04:00
module_signing.c
MODSIGN: Export module signature definitions
2019-08-05 18:39:56 -04:00
module-internal.h
…
module.c
Modules updates for v5.7
2020-04-09 12:52:34 -07:00
notifier.c
x86/mm: split vmalloc_sync_all()
2020-03-21 18:56:06 -07:00
nsproxy.c
ns: Introduce Time Namespace
2020-01-14 12:20:48 +01:00
padata.c
crypto: pcrypt - simplify error handling in pcrypt_create_aead()
2020-03-06 12:28:24 +11:00
panic.c
locking/refcount: Remove unused 'refcount_error_report()' function
2019-11-25 09:15:42 +01:00
params.c
lockdown: Lock down module params that specify hardware parameters (eg. ioport)
2019-08-19 21:54:16 -07:00
pid_namespace.c
pid: Improve the comment about waiting in zap_pid_ns_processes
2020-02-28 16:29:12 -06:00
pid.c
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
2020-04-10 12:59:56 -07:00
profile.c
proc: convert everything to "struct proc_ops"
2020-02-04 03:05:26 +00:00
ptrace.c
ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()
2020-01-18 13:51:39 +01:00
range.c
…
reboot.c
…
relay.c
…
resource.c
mm/memory_hotplug.c: use PFN_UP / PFN_DOWN in walk_system_ram_range()
2019-09-24 15:54:09 -07:00
rseq.c
rseq: Reject unknown flags on rseq unregister
2019-12-25 10:41:20 +01:00
seccomp.c
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next
2020-03-31 17:29:33 -07:00
signal.c
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
2020-04-23 13:30:18 -07:00
smp.c
cpu/hotplug: Move bringup of secondary CPUs out of smp_init()
2020-03-25 12:59:37 +01:00
smpboot.c
…
smpboot.h
…
softirq.c
lockdep: Rename trace_{hard,soft}{irq_context,irqs_enabled}()
2020-03-21 16:03:54 +01:00
stackleak.c
…
stacktrace.c
stacktrace: Get rid of unneeded '!!' pattern
2019-11-11 10:30:59 +01:00
stop_machine.c
stop_machine: Make stop_cpus() static
2020-01-17 10:19:21 +01:00
sys_ni.c
y2038: allow disabling time32 system calls
2019-11-15 14:38:30 +01:00
sys.c
sys/sysinfo: Respect boottime inside time namespace
2020-03-03 19:34:32 +01:00
sysctl_binary.c
sysctl: Remove the sysctl system call
2019-11-26 13:03:56 -06:00
sysctl-test.c
kunit: allow kunit tests to be loaded as a module
2020-01-09 16:42:29 -07:00
sysctl.c
mm/compaction: Disable compact_unevictable_allowed on RT
2020-04-02 09:35:31 -07:00
task_work.c
task_work_run: don't take ->pi_lock unconditionally
2020-03-02 14:06:33 -07:00
taskstats.c
taskstats: fix data-race
2019-12-04 15:18:39 +01:00
test_kprobes.c
…
torture.c
CPU (hotplug) updates:
2020-03-30 18:06:39 -07:00
tracepoint.c
The main changes in this release include:
2019-07-18 11:51:00 -07:00
tsacct.c
tsacct: add 64-bit btime field
2019-12-18 18:07:31 +01:00
ucount.c
ucount: Make sure ucounts in /proc/sys/user don't regress again
2020-04-07 21:51:27 +02:00
uid16.c
…
uid16.h
…
umh.c
coredump: fix crash when umh is disabled
2020-04-28 17:54:13 +02:00
up.c
smp/up: Make smp_call_function_single() match SMP semantics
2020-02-07 15:34:12 +01:00
user_namespace.c
Keyrings namespacing
2019-07-08 19:36:47 -07:00
user-return-notifier.c
…
user.c
Keyrings namespacing
2019-07-08 19:36:47 -07:00
utsname_sysctl.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441
2019-06-05 17:37:17 +02:00
utsname.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441
2019-06-05 17:37:17 +02:00
watchdog_hld.c
…
watchdog.c
watchdog/softlockup: Enforce that timestamp is valid on boot
2020-01-17 11:19:22 +01:00
workqueue_internal.h
…
workqueue.c
workqueue: Remove the warning in wq_worker_sleeping()
2020-04-08 11:35:20 +02:00