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@xxxxxxxxxxxxxxx
> Fixes: a3fdf784780c ("kunit: string-stream: Decouple string_stream from kunit")
> Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
> ---
> 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;
+ }
}
void kunit_debugfs_destroy_suite(struct kunit_suite *suite)
> }
>
> static void resource_free_string_stream(void *p)
> --
> 2.34.1
>
>
