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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: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemg200008.china.huawei.com (7.202.181.35) On 2024/11/9 21:02, Kuan-Wei Chiu wrote: > On Sat, Nov 09, 2024 at 08:40:30PM +0800, 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. >> > BTW, since alloc_string_stream() returns -ENOMEM on error rather than > NULL, it's best for the caller to check it with IS_ERR() instead of > IS_ERR_OR_NULL(). It's not a big issue, but I can send a cleanup patch > later to address this. Yes, I also notice it, but It's not a big issue. Thank you very much! > > Regards, > Kuan-Wei