Re: [PATCH 2/2] tracing: kprobe: Fix potential null-ptr-deref on trace_array in kprobe_event_gen_test_exit()
From: shangxiaojing
Date: Mon Nov 07 2022 - 08:47:20 EST
Hi,
On 2022/11/7 21:38, Masami Hiramatsu (Google) wrote:
Hi,
On Mon, 7 Nov 2022 15:16:17 +0800
Shang XiaoJing <shangxiaojing@xxxxxxxxxx> wrote:
When test_gen_kprobe_cmd() failed after kprobe_event_gen_cmd_end(), it
will goto delete, which will call kprobe_event_delete() and release the
corresponding resource. However, the trace_array in gen_kretprobe_test
will point to the invalid resource. Set gen_kretprobe_test->tr to NULL
after called kprobe_event_delete() and add NULL check when releasing
the module.
BUG: kernel NULL pointer dereference, address: 0000000000000070
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
CPU: 0 PID: 246 Comm: modprobe Tainted: G W
6.1.0-rc1-00174-g9522dc5c87da-dirty #248
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
RIP: 0010:__ftrace_set_clr_event_nolock+0x53/0x1b0
Code: e8 82 26 fc ff 49 8b 1e c7 44 24 0c ea ff ff ff 49 39 de 0f 84 3c
01 00 00 c7 44 24 18 00 00 00 00 e8 61 26 fc ff 48 8b 6b 10 <44> 8b 65
70 4c 8b 6d 18 41 f7 c4 00 02 00 00 75 2f
RSP: 0018:ffffc9000159fe00 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff88810971d268 RCX: 0000000000000000
RDX: ffff8881080be600 RSI: ffffffff811b48ff RDI: ffff88810971d058
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
R10: ffffc9000159fe58 R11: 0000000000000001 R12: ffffffffa0001064
R13: ffffffffa000106c R14: ffff88810971d238 R15: 0000000000000000
FS: 00007f89eeff6540(0000) GS:ffff88813b600000(0000)
knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000070 CR3: 000000010599e004 CR4: 0000000000330ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__ftrace_set_clr_event+0x3e/0x60
trace_array_set_clr_event+0x35/0x50
? 0xffffffffa0000000
kprobe_event_gen_test_exit+0xcd/0x10b [kprobe_event_gen_test]
__x64_sys_delete_module+0x206/0x380
? lockdep_hardirqs_on_prepare+0xd8/0x190
? syscall_enter_from_user_mode+0x1c/0x50
do_syscall_64+0x3f/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f89eeb061b7
Fixes: 64836248dda2 ("tracing: Add kprobe event command generation test module")
Signed-off-by: Shang XiaoJing <shangxiaojing@xxxxxxxxxx>
---
kernel/trace/kprobe_event_gen_test.c | 29 +++++++++++++++++-----------
1 file changed, 18 insertions(+), 11 deletions(-)
diff --git a/kernel/trace/kprobe_event_gen_test.c b/kernel/trace/kprobe_event_gen_test.c
index 1c98fafcf333..277e21e4a63e 100644
--- a/kernel/trace/kprobe_event_gen_test.c
+++ b/kernel/trace/kprobe_event_gen_test.c
@@ -145,6 +145,8 @@ static int __init test_gen_kprobe_cmd(void)
delete:
/* We got an error after creating the event, delete it */
ret = kprobe_event_delete("gen_kprobe_test");
+ if (trace_event_file_is_valid(gen_kprobe_test))
+ gen_kprobe_test->tr = NULL;
I think the correct fix should be
if (trace_event_file_is_valid(gen_kprobe_test)) {
trace_put_event_file(gen_kprobe_test);
gen_kprobe_test = NULL;
}
ret = kprobe_event_delete("gen_kprobe_test");
Since the gen_kprobe_event is owned by ftrace subsystem, the test
code should not change the tr field.
When trace_array_set_clr_event() failed, it already called
trace_put_event_file(), maybe we only need set gen_kprobe_test to NULL.
goto out;
}
@@ -208,6 +210,8 @@ static int __init test_gen_kretprobe_cmd(void)
delete:
/* We got an error after creating the event, delete it */
ret = kprobe_event_delete("gen_kretprobe_test");
+ if (trace_event_file_is_valid(gen_kretprobe_test))
+ gen_kretprobe_test->tr = NULL;
Ditto. >
And then, below changes are not required.
Yes, will fix in v2, thanks for the review.
Thanks,
--
Shang XiaoJing