When CONFIG_KFENCE_NUM_OBJECTS is set to a big number, kfence
kunit-test-case test_gfpzero will eat up nearly all the CPU's resources
and rcu_stall is reported as the following log which is cut from a
physical server.
rcu: INFO: rcu_sched self-detected stall on CPU
rcu: 68-....: (14422 ticks this GP) idle=6ce/1/0x4000000000000002
softirq=592/592 fqs=7500 (t=15004 jiffies g=10677 q=20019)
Task dump for CPU 68:
task:kunit_try_catch state:R running task
stack: 0 pid: 9728 ppid: 2 flags:0x0000020a
Call trace:
dump_backtrace+0x0/0x1e4
show_stack+0x20/0x2c
sched_show_task+0x148/0x170
...
rcu_sched_clock_irq+0x70/0x180
update_process_times+0x68/0xb0
tick_sched_handle+0x38/0x74
...
gic_handle_irq+0x78/0x2c0
el1_irq+0xb8/0x140
kfree+0xd8/0x53c
test_alloc+0x264/0x310 [kfence_test]
test_gfpzero+0xf4/0x840 [kfence_test]
kunit_try_run_case+0x48/0x20c
kunit_generic_run_threadfn_adapter+0x28/0x34
kthread+0x108/0x13c
ret_from_fork+0x10/0x18
To avoid rcu_stall and unacceptable latency, a schedule point is
added to test_gfpzero.
Link: https://lkml.kernel.org/r/20220309083753.1561921-4-liupeng256@huawei.com
Signed-off-by: Peng Liu <liupeng256@huawei.com>
Reviewed-by: Marco Elver <elver@google.com>
Tested-by: Brendan Higgins <brendanhiggins@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Wang Kefeng <wangkefeng.wang@huawei.com>
Cc: Daniel Latypov <dlatypov@google.com>
Cc: David Gow <davidgow@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "kunit: fix a UAF bug and do some optimization", v2.
This series is to fix UAF (use after free) when running kfence test case
test_gfpzero, which is time costly. This UAF bug can be easily triggered
by setting CONFIG_KFENCE_NUM_OBJECTS = 65535. Furthermore, some
optimization for kunit tests has been done.
This patch (of 3):
Kunit will create a new thread to run an actual test case, and the main
process will wait for the completion of the actual test thread until
overtime. The variable "struct kunit test" has local property in function
kunit_try_catch_run, and will be used in the test case thread. Task
kunit_try_catch_run will free "struct kunit test" when kunit runs
overtime, but the actual test case is still run and an UAF bug will be
triggered.
The above problem has been both observed in a physical machine and qemu
platform when running kfence kunit tests. The problem can be triggered
when setting CONFIG_KFENCE_NUM_OBJECTS = 65535. Under this setting, the
test case test_gfpzero will cost hours and kunit will run to overtime.
The follows show the panic log.
BUG: unable to handle page fault for address: ffffffff82d882e9
Call Trace:
kunit_log_append+0x58/0xd0
...
test_alloc.constprop.0.cold+0x6b/0x8a [kfence_test]
test_gfpzero.cold+0x61/0x8ab [kfence_test]
kunit_try_run_case+0x4c/0x70
kunit_generic_run_threadfn_adapter+0x11/0x20
kthread+0x166/0x190
ret_from_fork+0x22/0x30
Kernel panic - not syncing: Fatal exception
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
Ubuntu-1.8.2-1ubuntu1 04/01/2014
To solve this problem, the test case thread should be stopped when the
kunit frame runs overtime. The stop signal will send in function
kunit_try_catch_run, and test_gfpzero will handle it.
Link: https://lkml.kernel.org/r/20220309083753.1561921-1-liupeng256@huawei.com
Link: https://lkml.kernel.org/r/20220309083753.1561921-2-liupeng256@huawei.com
Signed-off-by: Peng Liu <liupeng256@huawei.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Tested-by: Brendan Higgins <brendanhiggins@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Wang Kefeng <wangkefeng.wang@huawei.com>
Cc: Daniel Latypov <dlatypov@google.com>
Cc: David Gow <davidgow@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge more updates from Andrew Morton:
"147 patches, based on 7d2a07b769.
Subsystems affected by this patch series: mm (memory-hotplug, rmap,
ioremap, highmem, cleanups, secretmem, kfence, damon, and vmscan),
alpha, percpu, procfs, misc, core-kernel, MAINTAINERS, lib,
checkpatch, epoll, init, nilfs2, coredump, fork, pids, criu, kconfig,
selftests, ipc, and scripts"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (94 commits)
scripts: check_extable: fix typo in user error message
mm/workingset: correct kernel-doc notations
ipc: replace costly bailout check in sysvipc_find_ipc()
selftests/memfd: remove unused variable
Kconfig.debug: drop selecting non-existing HARDLOCKUP_DETECTOR_ARCH
configs: remove the obsolete CONFIG_INPUT_POLLDEV
prctl: allow to setup brk for et_dyn executables
pid: cleanup the stale comment mentioning pidmap_init().
kernel/fork.c: unexport get_{mm,task}_exe_file
coredump: fix memleak in dump_vma_snapshot()
fs/coredump.c: log if a core dump is aborted due to changed file permissions
nilfs2: use refcount_dec_and_lock() to fix potential UAF
nilfs2: fix memory leak in nilfs_sysfs_delete_snapshot_group
nilfs2: fix memory leak in nilfs_sysfs_create_snapshot_group
nilfs2: fix memory leak in nilfs_sysfs_delete_##name##_group
nilfs2: fix memory leak in nilfs_sysfs_create_##name##_group
nilfs2: fix NULL pointer in nilfs_##name##_attr_release
nilfs2: fix memory leak in nilfs_sysfs_create_device_group
trap: cleanup trap_init()
init: move usermodehelper_enable() to populate_rootfs()
...
kfence_test_init and kunit_init both use the same level late_initcall,
which means if kfence_test_init linked ahead of kunit_init,
kfence_test_init will get a NULL debugfs_rootdir as parent dentry, then
kfence_test_init and kfence_debugfs_init both create a debugfs node
named "kfence" under debugfs_mount->mnt_root, and it will throw out
"debugfs: Directory 'kfence' with parent '/' already present!" with
EEXIST. So kfence_test_init should be deferred.
Link: https://lkml.kernel.org/r/20210714113140.2949995-1-o451686892@gmail.com
Signed-off-by: Weizhao Ouyang <o451686892@gmail.com>
Tested-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
