linux-kernel - Re: [PATCH v2] kunit: string-stream: Fix a UAF bug in kunit_init

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Message-ID: <ZzwlxMbDH64S6geV@visitorckw-System-Product-Name>
Date: Tue, 19 Nov 2024 13:44:36 +0800
From: Kuan-Wei Chiu <visitorckw@...il.com>
To: Jinjie Ruan <ruanjinjie@...wei.com>
Cc: brendan.higgins@...ux.dev, davidgow@...gle.com, 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 v2] kunit: string-stream: Fix a UAF bug in
 kunit_init_suite()

On Tue, Nov 12, 2024 at 04:03:14PM +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, 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 to fix it.

I just noticed that since v2, we no longer set the stream pointer to
NULL but instead set suite->log to NULL. This description needs a
slight adjustment.

Regards,
Kuan-Wei

> 	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")
> Suggested-by: Kuan-Wei Chiu <visitorckw@...il.com>
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> ---
> v2:
> - Correct the fix way.
> - Add Suggested-by.
> ---
>  lib/kunit/debugfs.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> 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;
> +	}
>  }
>  
>  void kunit_debugfs_destroy_suite(struct kunit_suite *suite)
> -- 
> 2.34.1
>