The patch titled
Subject: kunit: fix UAF when run kfence test case test_gfpzero
has been added to the -mm tree. Its filename is
kunit-fix-uaf-when-run-kfence-test-case-test_gfpzero.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/kunit-fix-uaf-when-run-kfence-test-case-test_gfpzero.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/kunit-fix-uaf-when-run-kfence-test-case-test_gfpzero.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Peng Liu <liupeng256@xxxxxxxxxx>
Subject: kunit: fix UAF when run kfence test case test_gfpzero
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@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20220309083753.1561921-2-liupeng256@xxxxxxxxxx
Signed-off-by: Peng Liu <liupeng256@xxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Brendan Higgins <brendanhiggins@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Wang Kefeng <wangkefeng.wang@xxxxxxxxxx>
Cc: Daniel Latypov <dlatypov@xxxxxxxxxx>
Cc: David Gow <davidgow@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/kunit/try-catch.c | 1 +
mm/kfence/kfence_test.c | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)
--- a/lib/kunit/try-catch.c~kunit-fix-uaf-when-run-kfence-test-case-test_gfpzero
+++ a/lib/kunit/try-catch.c
@@ -78,6 +78,7 @@ void kunit_try_catch_run(struct kunit_tr
if (time_remaining == 0) {
kunit_err(test, "try timed out\n");
try_catch->try_result = -ETIMEDOUT;
+ kthread_stop(task_struct);
}
exit_code = try_catch->try_result;
--- a/mm/kfence/kfence_test.c~kunit-fix-uaf-when-run-kfence-test-case-test_gfpzero
+++ a/mm/kfence/kfence_test.c
@@ -623,7 +623,7 @@ static void test_gfpzero(struct kunit *t
break;
test_free(buf2);
- if (i == CONFIG_KFENCE_NUM_OBJECTS) {
+ if (kthread_should_stop() || (i == CONFIG_KFENCE_NUM_OBJECTS)) {
kunit_warn(test, "giving up ... cannot get same object back\n");
return;
}
_
Patches currently in -mm which might be from liupeng256@xxxxxxxxxx are
kunit-fix-uaf-when-run-kfence-test-case-test_gfpzero.patch
kunit-make-kunit_test_timeout-compatible-with-comment.patch
kfence-test-try-to-avoid-test_gfpzero-trigger-rcu_stall.patch
