linux/kernel
Luis Chamberlain f3a6bc0d47 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 07:57:21 +02:00
..
bpf cpumap: Avoid warning when CONFIG_DEBUG_PER_CPU_MAPS is enabled 2020-05-02 17:25:53 +02:00
cgroup cgroup1: don't call release_agent when it is "" 2020-04-02 15:28:14 +02:00
configs kconfig: tinyconfig: remove stale stack protector fixups 2018-06-15 07:15:28 +09:00
debug kdb: do a sanity check on the cpu in kdb_per_cpu() 2020-01-27 14:50:48 +01:00
dma dma-debug: add a schedule point in debug_dma_dump_mappings() 2020-01-04 19:12:43 +01:00
events perf/core: fix parent pid/tid in task exit events 2020-05-02 17:25:53 +02:00
gcov kernel/gcov/fs.c: gcov_seq_next() should increase position index 2020-04-29 16:31:12 +02:00
irq genirq/irqdomain: Check pointer in irq_domain_alloc_irqs_hierarchy() 2020-04-17 10:48:41 +02:00
livepatch livepatch: Nullify obj->mod in klp_module_coming()'s error path 2019-10-07 18:57:10 +02:00
locking locktorture: Print ratio of acquisitions, not failures 2020-04-23 10:30:23 +02:00
power PM: hibernate: Freeze kernel threads in software_resume() 2020-05-06 08:13:28 +02:00
printk printk: fix exclusive_console replaying 2020-02-11 04:33:51 -08:00
rcu rcu: Avoid data-race in rcu_gp_fqs_check_wake() 2020-02-11 04:33:55 -08:00
sched sched: Avoid scale real weight down to zero 2020-04-17 10:48:40 +02:00
time clocksource: Prevent double add_timer_on() for watchdog_timer 2020-02-11 04:34:18 -08:00
trace tracing: Add a vmalloc_sync_mappings() for safe measure 2020-05-14 07:57:20 +02:00
.gitignore
acct.c acct_on(): don't mess with freeze protection 2019-05-31 06:46:05 -07:00
async.c
audit_fsnotify.c fsnotify: add fsnotify_add_inode_mark() wrappers 2018-05-18 14:58:22 +02:00
audit_tree.c audit: Embed key into chunk 2019-12-13 08:51:11 +01:00
audit_watch.c audit_get_nd(): don't unlock parent too early 2019-12-13 08:51:02 +01:00
audit.c audit: check the length of userspace generated audit records 2020-04-29 16:31:31 +02:00
audit.h
auditfilter.c audit: fix error handling in audit_data_to_entry() 2020-03-05 16:42:17 +01:00
auditsc.c audit: print empty EXECVE args 2019-12-01 09:17:17 +01:00
backtracetest.c
bounds.c kbuild: fix kernel/bounds.c 'W=1' warning 2018-11-13 11:08:47 -08:00
capability.c LSM: generalize flag passing to security_capable 2020-01-23 08:21:29 +01:00
compat.c time: Enable get/put_compat_itimerspec64 always 2018-06-24 14:39:47 +02:00
configs.c
context_tracking.c
cpu_pm.c
cpu.c x86/speculation: Remove redundant arch_smt_update() invocation 2020-04-17 10:48:50 +02:00
crash_core.c kernel/crash_core.c: print timestamp using time64_t 2018-08-22 10:52:47 -07:00
crash_dump.c
cred.c memcg: account security cred as well to kmemcg 2020-01-09 10:19:00 +01:00
delayacct.c
dma.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
elfcore.c kernel/elfcore.c: include proper prototypes 2019-10-11 18:21:23 +02:00
exec_domain.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
exit.c exit: panic before exit_mm() on global init exit 2020-01-09 10:19:02 +01:00
extable.c
fail_function.c bpf/error-inject/kprobes: Clear current_kprobe and enable preempt in kprobe 2018-06-21 12:33:19 +02:00
fork.c fork,memcg: alloc_thread_stack_node needs to set tsk->stack 2020-01-27 14:50:58 +01:00
freezer.c PM / reboot: Eliminate race between reboot and suspend 2018-08-06 12:35:20 +02:00
futex.c futex: Unbreak futex hashing 2020-03-25 08:06:14 +01:00
groups.c
hung_task.c kernel: hung_task.c: disable on suspend 2019-04-20 09:16:02 +02:00
iomem.c memremap: split devm_memremap_pages() and memremap() infrastructure 2018-05-15 23:08:33 -07:00
irq_work.c irq_work: Do not raise an IPI when queueing work on the local CPU 2019-05-31 06:46:19 -07:00
jump_label.c jump_label: move 'asm goto' support test to Kconfig 2019-06-04 08:02:34 +02:00
kallsyms.c kallsyms: Don't let kallsyms_lookup_size_offset() fail on retrieving the first symbol 2019-09-21 07:17:02 +02:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt kconfig: include kernel/Kconfig.preempt from init/Kconfig 2018-08-02 08:06:54 +09:00
kcov.c kernel/kcov.c: mark write_comp_data() as notrace 2019-02-12 19:47:20 +01:00
kexec_core.c kexec: Allocate decrypted control pages for kdump if SME is enabled 2019-11-24 08:20:29 +01:00
kexec_file.c treewide: Use array_size() in vzalloc() 2018-06-12 16:19:22 -07:00
kexec_internal.h
kexec.c kexec: add call to LSM hook in original kexec_load syscall 2018-07-16 12:31:57 -07:00
kmod.c kmod: make request_module() return an error when autoloading is disabled 2020-04-17 10:48:52 +02:00
kprobes.c kprobes: Fix optimize_kprobe()/unoptimize_kprobe() cancellation logic 2020-03-11 14:14:47 +01:00
ksysfs.c
kthread.c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-08-13 11:25:07 -07:00
latencytop.c
Makefile y2038: futex: Move compat implementation into futex.c 2019-12-01 09:17:38 +01:00
memremap.c mm/memory_hotplug: shrink zones when offlining memory 2020-01-29 16:43:27 +01:00
module_signing.c modsign: log module name in the event of an error 2018-07-02 11:36:17 +02:00
module-internal.h modsign: log module name in the event of an error 2018-07-02 11:36:17 +02:00
module.c module: avoid setting info->name early in case we can fall back to info->mod->name 2020-02-24 08:34:49 +01:00
notifier.c x86/mm: split vmalloc_sync_all() 2020-03-25 08:06:13 +01:00
nsproxy.c
padata.c padata: always acquire cpu_hotplug_lock before pinst->lock 2020-04-13 10:45:05 +02:00
panic.c kernel/panic.c: do not append newline to the stack protector panic string 2019-12-01 09:17:10 +01:00
params.c
pid_namespace.c signal/pid_namespace: Fix reboot_pid_ns to use send_sig not force_sig 2019-07-26 09:14:01 +02:00
pid.c Fix failure path in alloc_pid() 2019-01-13 09:51:06 +01:00
profile.c
ptrace.c ptrace: reintroduce usage of subjective credentials in ptrace_has_cap() 2020-01-23 08:21:29 +01:00
range.c
reboot.c PM / reboot: Eliminate race between reboot and suspend 2018-08-06 12:35:20 +02:00
relay.c relay: check return of create_buf_file() properly 2019-03-13 14:02:35 -07:00
resource.c resource: fix locking in find_next_iomem_res() 2019-09-16 08:22:20 +02:00
rseq.c rseq: uapi: Declare rseq_cs field as union, update includes 2018-07-10 22:18:52 +02:00
seccomp.c LSM: generalize flag passing to security_capable 2020-01-23 08:21:29 +01:00
signal.c signal: Extend exec_id to 64bits 2020-04-17 10:48:47 +02:00
smp.c cpu/hotplug: Fix "SMT disabled by BIOS" detection for KVM 2019-02-12 19:47:25 +01:00
smpboot.c smpboot: Remove cpumask from the API 2018-07-03 09:20:44 +02:00
smpboot.h
softirq.c nohz: Fix missing tick reprogram when interrupting an inline softirq 2018-08-03 15:52:10 +02:00
stacktrace.c
stop_machine.c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-08-13 11:25:07 -07:00
sys_ni.c Merge branch 'core-rseq-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-06-10 10:17:09 -07:00
sys.c kernel/sys.c: prctl: fix false positive in validate_prctl_map() 2019-06-15 11:54:01 +02:00
sysctl_binary.c
sysctl.c kernel: sysctl: make drop_caches write-only 2020-01-04 19:13:17 +01:00
task_work.c
taskstats.c taskstats: fix data-race 2020-01-09 10:18:59 +01:00
test_kprobes.c kprobes: Remove jprobe API implementation 2018-06-21 12:33:05 +02:00
torture.c torture: Keep old-school dmesg format 2018-06-25 11:30:10 -07:00
tracepoint.c tracepoint: Fix tracepoint array element size mismatch 2018-10-17 15:35:29 -04:00
tsacct.c
ucount.c
uid16.c
uid16.h
umh.c coredump: fix crash when umh is disabled 2020-05-14 07:57:21 +02:00
up.c
user_namespace.c userns: also map extents in the reverse map to kernel IDs 2018-11-13 11:09:00 -08:00
user-return-notifier.c
user.c userns: use irqsave variant of refcount_dec_and_lock() 2018-08-22 10:52:47 -07:00
utsname_sysctl.c sys: don't hold uts_sem while accessing userspace memory 2018-08-11 02:05:53 -05:00
utsname.c
watchdog_hld.c watchdog: Mark watchdog touch functions as notrace 2018-08-30 12:56:40 +02:00
watchdog.c watchdog/softlockup: Enforce that timestamp is valid on boot 2020-02-24 08:34:49 +01:00
workqueue_internal.h workqueue: Set worker->desc to workqueue name by default 2018-05-18 08:47:13 -07:00
workqueue.c workqueue: don't use wq_select_unbound_cpu() for bound works 2020-03-18 07:14:20 +01:00