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Luis Chamberlain 480534e030 coredump: fix crash when umh is disabled 
commit 3740d93e37 upstream.

Commit 64e90a8acb ("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: 64e90a8acb ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-05-14 07:58:27 +02:00
..
bpf
cpumap: Avoid warning when CONFIG_DEBUG_PER_CPU_MAPS is enabled
2020-05-02 08:48:51 +02:00
cgroup
cgroup1: don't call release_agent when it is ""
2020-04-01 11:01:51 +02:00
configs
…
debug
kgdb: don't use a notifier to enter kgdb at panic; call directly
2019-09-25 17:51:40 -07:00
dma
dma-direct: fix data truncation in dma_direct_get_required_mask()
2020-04-29 16:33:00 +02:00
events
perf/core: fix parent pid/tid in task exit events
2020-05-02 08:48:52 +02:00
gcov
kernel/gcov/fs.c: gcov_seq_next() should increase position index
2020-04-29 16:33:00 +02:00
irq
genirq/debugfs: Add missing sanity checks to interrupt injection
2020-04-17 10:50:11 +02:00
livepatch
livepatch: Nullify obj->mod in klp_module_coming()'s error path
2019-08-19 13:03:37 +02:00
locking
locktorture: Print ratio of acquisitions, not failures
2020-04-23 10:36:44 +02:00
power
PM: hibernate: Freeze kernel threads in software_resume()
2020-05-06 08:15:09 +02:00
printk
printk: queue wake_up_klogd irq_work only if per-CPU areas are ready
2020-05-02 08:48:42 +02:00
rcu
rcu: Allow only one expedited GP to run concurrently with wakeups
2020-03-05 16:43:50 +01:00
sched
sched/core: Fix reset-on-fork from RT with uclamp
2020-05-02 08:48:52 +02:00
time
time/sched_clock: Expire timer in hardirq context
2020-04-17 10:50:02 +02:00
trace
tracing: Add a vmalloc_sync_mappings() for safe measure
2020-05-14 07:58:25 +02:00
.gitignore
Provide in-kernel headers to make extending kernel easier
2019-04-29 16:48:03 +02:00
acct.c
acct_on(): don't mess with freeze protection
2019-04-04 21:04:13 -04:00
async.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441
2019-06-05 17:37:17 +02:00
audit_fsnotify.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157
2019-05-30 11:26:37 -07:00
audit_tree.c
fsnotify: switch send_to_group() and ->handle_event to const struct qstr *
2019-04-26 13:51:03 -04:00
audit_watch.c
audit_get_nd(): don't unlock parent too early
2019-11-10 11:56:55 -05:00
audit.c
audit: check the length of userspace generated audit records
2020-04-29 16:33:18 +02:00
audit.h
Merge tag 'audit-pr-20190702' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit
2019-07-08 18:55:42 -07:00
auditfilter.c
audit: fix error handling in audit_data_to_entry()
2020-03-05 16:43:42 +01:00
auditsc.c
audit: enforce op for string fields
2019-05-28 17:46:43 -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
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500
2019-06-19 17:09:55 +02:00
configs.c
kernel/configs: Replace GPL boilerplate code with SPDX identifier
2019-07-30 18:34:15 +02:00
context_tracking.c
treewide: Add SPDX license identifier for missed files
2019-05-21 10:50:45 +02:00
cpu_pm.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 282
2019-06-05 17:36:37 +02:00
cpu.c
cpu/hotplug: Ignore pm_wakeup_pending() for disable_nonboot_cpus()
2020-04-17 10:50:11 +02:00
crash_core.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 230
2019-06-19 17:09:06 +02:00
crash_dump.c
treewide: Add SPDX license identifier for missed files
2019-05-21 10:50:45 +02:00
cred.c
keys: Fix request_key() cache
2020-01-17 19:48:42 +01:00
delayacct.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 25
2019-05-21 11:52:39 +02:00
dma.c
…
elfcore.c
kernel/elfcore.c: include proper prototypes
2019-09-25 17:51:39 -07:00
exec_domain.c
…
exit.c
exit: panic before exit_mm() on global init exit
2020-01-09 10:20:01 +01:00
extable.c
extable: Add function to search only kernel exception table
2019-08-21 22:23:48 +10:00
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
mm: fork: fix kernel_stack memcg stats for various stack implementations
2020-04-01 11:02:03 +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
futex: Unbreak futex hashing
2020-03-25 08:25:58 +01:00
gen_kheaders.sh
kheaders: substituting --sort in archive creation
2019-10-17 09:08:19 +09:00
groups.c
…
hung_task.c
treewide: Add SPDX license identifier for missed files
2019-05-21 10:50:45 +02:00
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
treewide: Add SPDX license identifier for missed files
2019-05-21 10:50:45 +02:00
jump_label.c
jump_label: Don't warn on __exit jump entries
2019-08-29 15:10:10 +01:00
kallsyms.c
kallsyms: Don't let kallsyms_lookup_size_offset() fail on retrieving the first symbol
2019-08-27 16:19:56 +01:00
kcmp.c
…
Kconfig.freezer
treewide: Add SPDX license identifier - Makefile/Kconfig
2019-05-21 10:50:46 +02:00
Kconfig.hz
treewide: Add SPDX license identifier - Makefile/Kconfig
2019-05-21 10:50:46 +02:00
Kconfig.locks
treewide: Add SPDX license identifier - Makefile/Kconfig
2019-05-21 10:50:46 +02:00
Kconfig.preempt
sched/rt, Kconfig: Unbreak def/oldconfig with CONFIG_PREEMPT=y
2019-07-22 18:05:11 +02:00
kcov.c
…
kexec_core.c
kexec: bail out upon SIGKILL when allocating memory.
2019-09-25 17:51:40 -07:00
kexec_elf.c
kexec_elf: support 32 bit ELF files
2019-09-06 23:58:44 +02:00
kexec_file.c
Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security
2019-09-28 08:14:15 -07:00
kexec_internal.h
…
kexec.c
kexec_load: Disable at runtime if the kernel is locked down
2019-08-19 21:54:15 -07:00
kheaders.c
kheaders: Move from proc to sysfs
2019-05-24 20:16:01 +02:00
kmod.c
kmod: make request_module() return an error when autoloading is disabled
2020-04-17 10:50:22 +02:00
kprobes.c
kprobes: Fix optimize_kprobe()/unoptimize_kprobe() cancellation logic
2020-03-12 13:00:09 +01:00
ksysfs.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 170
2019-05-30 11:26:39 -07:00
kthread.c
kthread: make __kthread_queue_delayed_work static
2019-10-16 09:20:58 -07:00
latencytop.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441
2019-06-05 17:37:17 +02:00
Makefile
Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity
2019-09-27 19:37:27 -07:00
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
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36
2019-05-24 17:27:11 +02:00
module.c
module: avoid setting info->name early in case we can fall back to info->mod->name
2020-02-24 08:36:54 +01:00
notifier.c
x86/mm: split vmalloc_sync_all()
2020-03-25 08:25:58 +01:00
nsproxy.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441
2019-06-05 17:37:17 +02:00
padata.c
padata: always acquire cpu_hotplug_lock before pinst->lock
2020-04-08 09:08:47 +02:00
panic.c
panic: ensure preemption is disabled during panic()
2019-10-07 15:47:19 -07:00
params.c
lockdown: Lock down module params that specify hardware parameters (eg. ioport)
2019-08-19 21:54:16 -07:00
pid_namespace.c
proc/sysctl: add shared variables for range check
2019-07-18 17:08:07 -07:00
pid.c
kernel/pid.c: convert struct pid count to refcount_t
2019-07-16 19:23:24 -07:00
profile.c
treewide: Add SPDX license identifier for missed files
2019-05-21 10:50:45 +02:00
ptrace.c
ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()
2020-01-23 08:22:36 +01:00
range.c
…
reboot.c
treewide: Add SPDX license identifier for missed files
2019-05-21 10:50:45 +02:00
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
signal: Remove task parameter from force_sig
2019-05-27 09:36:28 -05:00
seccomp.c
seccomp: Add missing compat_ioctl for notify
2020-04-17 10:50:09 +02:00
signal.c
signal: check sig before setting info in kill_pid_usb_asyncio
2020-05-02 08:48:55 +02:00
smp.c
smp: Warn on function calls from softirq context
2019-07-20 11:27:16 +02:00
smpboot.c
treewide: Add SPDX license identifier for missed files
2019-05-21 10:50:45 +02:00
smpboot.h
…
softirq.c
Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2019-07-08 11:01:13 -07:00
stackleak.c
…
stacktrace.c
stacktrace: Don't skip first entry on noncurrent tasks
2019-11-04 21:19:25 +01:00
stop_machine.c
stop_machine: Avoid potential race behaviour
2019-10-17 12:47:12 +02:00
sys_ni.c
arch: handle arches who do not yet define clone3
2019-06-21 01:54:53 +02:00
sys.c
Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2019-09-17 12:35:15 -07:00
sysctl_binary.c
…
sysctl.c
kernel: sysctl: make drop_caches write-only
2020-01-04 19:18:32 +01:00
task_work.c
…
taskstats.c
taskstats: fix data-race
2020-01-09 10:19:54 +01:00
test_kprobes.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 25
2019-05-21 11:52:39 +02:00
torture.c
torture: Remove exporting of internal functions
2019-08-01 14:30:22 -07:00
tracepoint.c
Merge tag 'trace-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
2019-07-18 11:51:00 -07:00
tsacct.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157
2019-05-30 11:26:37 -07:00
ucount.c
proc/sysctl: add shared variables for range check
2019-07-18 17:08:07 -07:00
uid16.c
…
uid16.h
…
umh.c
coredump: fix crash when umh is disabled
2020-05-14 07:58:27 +02:00
up.c
smp: Remove smp_call_function() and on_each_cpu() return values
2019-06-23 14:26:26 +02:00
user_namespace.c
Merge tag 'keys-namespace-20190627' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs
2019-07-08 19:36:47 -07:00
user-return-notifier.c
treewide: Add SPDX license identifier for missed files
2019-05-21 10:50:45 +02:00
user.c
Merge tag 'keys-namespace-20190627' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs
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
kernel/watchdog_hld.c: hard lockup message should end with a newline
2019-04-19 09:46:05 -07:00
watchdog.c
watchdog/softlockup: Enforce that timestamp is valid on boot
2020-02-24 08:36:52 +01:00
workqueue_internal.h
sched/core, workqueues: Distangle worker accounting from rq lock
2019-04-16 16:55:15 +02:00
workqueue.c
workqueue: don't use wq_select_unbound_cpu() for bound works
2020-03-18 07:17:50 +01:00