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Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.2.0 Subject: Re: [PATCH] kunit: string-stream: Fix a UAF bug in kunit_init_suite() Content-Language: en-US To: Kuan-Wei Chiu CC: , , , , , , , References: <20241024094303.1531810-1-ruanjinjie@huawei.com> From: Jinjie Ruan In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemg200008.china.huawei.com (7.202.181.35) On 2024/11/9 20:40, Kuan-Wei Chiu wrote: > Hi Jinjie, > > On Thu, Oct 24, 2024 at 05:43:03PM +0800, Jinjie Ruan wrote: >> In kunit_debugfs_create_suite(), if alloc_string_stream() fails in the >> kunit_suite_for_each_test_case() loop, the "suite->log = stream" >> has assigned before, and the error path only free the suite->log's stream >> memory but not set it to NULL in string_stream_destroy(), so the later >> string_stream_clear() of suite->log in kunit_init_suite() will cause >> below UAF bug. >> >> Set stream pointer to NULL after free in string_stream_destroy() >> to fix it. >> >> Unable to handle kernel paging request at virtual address 006440150000030d >> Mem abort info: >> ESR = 0x0000000096000004 >> EC = 0x25: DABT (current EL), IL = 32 bits >> SET = 0, FnV = 0 >> EA = 0, S1PTW = 0 >> FSC = 0x04: level 0 translation fault >> Data abort info: >> ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 >> CM = 0, WnR = 0, TnD = 0, TagAccess = 0 >> GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 >> [006440150000030d] address between user and kernel address ranges >> Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP >> Dumping ftrace buffer: >> (ftrace buffer empty) >> Modules linked in: iio_test_gts industrialio_gts_helper cfg80211 rfkill ipv6 [last unloaded: iio_test_gts] >> CPU: 5 UID: 0 PID: 6253 Comm: modprobe Tainted: G B W N 6.12.0-rc4+ #458 >> Tainted: [B]=BAD_PAGE, [W]=WARN, [N]=TEST >> Hardware name: linux,dummy-virt (DT) >> pstate: 40000005 (nZcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) >> pc : string_stream_clear+0x54/0x1ac >> lr : string_stream_clear+0x1a8/0x1ac >> sp : ffffffc080b47410 >> x29: ffffffc080b47410 x28: 006440550000030d x27: ffffff80c96b5e98 >> x26: ffffff80c96b5e80 x25: ffffffe461b3f6c0 x24: 0000000000000003 >> x23: ffffff80c96b5e88 x22: 1ffffff019cdf4fc x21: dfffffc000000000 >> x20: ffffff80ce6fa7e0 x19: 032202a80000186d x18: 0000000000001840 >> x17: 0000000000000000 x16: 0000000000000000 x15: ffffffe45c355cb4 >> x14: ffffffe45c35589c x13: ffffffe45c03da78 x12: ffffffb810168e75 >> x11: 1ffffff810168e74 x10: ffffffb810168e74 x9 : dfffffc000000000 >> x8 : 0000000000000004 x7 : 0000000000000003 x6 : 0000000000000001 >> x5 : ffffffc080b473a0 x4 : 0000000000000000 x3 : 0000000000000000 >> x2 : 0000000000000001 x1 : ffffffe462fbf620 x0 : dfffffc000000000 >> Call trace: >> string_stream_clear+0x54/0x1ac >> __kunit_test_suites_init+0x108/0x1d8 >> kunit_exec_run_tests+0xb8/0x100 >> kunit_module_notify+0x400/0x55c >> notifier_call_chain+0xfc/0x3b4 >> blocking_notifier_call_chain+0x68/0x9c >> do_init_module+0x24c/0x5c8 >> load_module+0x4acc/0x4e90 >> init_module_from_file+0xd4/0x128 >> idempotent_init_module+0x2d4/0x57c >> __arm64_sys_finit_module+0xac/0x100 >> invoke_syscall+0x6c/0x258 >> el0_svc_common.constprop.0+0x160/0x22c >> do_el0_svc+0x44/0x5c >> el0_svc+0x48/0xb8 >> el0t_64_sync_handler+0x13c/0x158 >> el0t_64_sync+0x190/0x194 >> Code: f9400753 d2dff800 f2fbffe0 d343fe7c (38e06b80) >> ---[ end trace 0000000000000000 ]--- >> Kernel panic - not syncing: Oops: Fatal exception >> >> Cc: stable@vger.kernel.org >> Fixes: a3fdf784780c ("kunit: string-stream: Decouple string_stream from kunit") >> Signed-off-by: Jinjie Ruan >> --- >> lib/kunit/string-stream.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/lib/kunit/string-stream.c b/lib/kunit/string-stream.c >> index 54f4fdcbfac8..00ad518b730b 100644 >> --- a/lib/kunit/string-stream.c >> +++ b/lib/kunit/string-stream.c >> @@ -178,6 +178,7 @@ void string_stream_destroy(struct string_stream *stream) >> >> string_stream_clear(stream); >> kfree(stream); >> + stream = NULL; > > Thanks for proposing the fix. However, I don't believe it fully > resolves the UAF issue. Changing the stream pointer value within > string_stream_destroy() doesn't update the caller's stream pointer, so > the issue remains. > > I think the correct approach would be to set the log pointer to NULL in > the error path of kunit_debugfs_create_suite() to address the issue. > Let me know if I've missed something or overlooked an obvious detail. > > Here's the proposed code: > > diff --git a/lib/kunit/debugfs.c b/lib/kunit/debugfs.c > index d548750a325a..b25d214b93e1 100644 > --- a/lib/kunit/debugfs.c > +++ b/lib/kunit/debugfs.c > @@ -212,8 +212,11 @@ void kunit_debugfs_create_suite(struct kunit_suite *suite) > > err: > string_stream_destroy(suite->log); > - kunit_suite_for_each_test_case(suite, test_case) > + suite->log = NULL; > + kunit_suite_for_each_test_case(suite, test_case) { > string_stream_destroy(test_case->log); > + test_case->log = NULL; > + } It looks fine, test it and if ok, will update it. > } > > void kunit_debugfs_destroy_suite(struct kunit_suite *suite) > > >> } >> >> static void resource_free_string_stream(void *p) >> -- >> 2.34.1 >> >>