linux-kernel - Re: [PATCH] kunit: string-stream: Fix a UAF bug in kunit_init

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Message-ID: <CABVgOSkBnO2pfo_wWyUiek-XVEEahB9druaTv3BeqK-WiDjMZA@mail.gmail.com>
Date: Sat, 9 Nov 2024 17:33:01 +0800
From: David Gow <davidgow@...gle.com>
To: Jinjie Ruan <ruanjinjie@...wei.com>
Cc: brendan.higgins@...ux.dev, rmoar@...gle.com, skhan@...uxfoundation.org, 
	rf@...nsource.cirrus.com, linux-kselftest@...r.kernel.org, 
	kunit-dev@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kunit: string-stream: Fix a UAF bug in kunit_init_suite()

On Thu, 24 Oct 2024 at 17:43, Jinjie Ruan <ruanjinjie@...wei.com> 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@...r.kernel.org
> Fixes: a3fdf784780c ("kunit: string-stream: Decouple string_stream from kunit")
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> ---

Nice catch, thanks.

Reviewed-by: David Gow <davidgow@...gle.com>

Cheers,
-- David

>  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;
>  }
>
>  static void resource_free_string_stream(void *p)
> --
> 2.34.1
>

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