Re: [PATCH 1/2] tracing: kprobe: Fix potential null-ptr-deref on trace_event_file in kprobe_event_gen_test_exit()

[shangxiaojing]

On 2022/11/7 21:25, Masami Hiramatsu (Google) wrote:
> On Mon, 7 Nov 2022 15:16:16 +0800
> Shang XiaoJing <shangxiaojing@xxxxxxxxxx> wrote:
>
> > When trace_get_event_file() failed, gen_kretprobe_test will be assigned
> > as the error code. If module kprobe_event_gen_test is removed now, the
> > null pointer dereference will happen in kprobe_event_gen_test_exit().
> > Check if gen_kprobe_test or gen_kretprobe_test is error code or NULL
> > before dereference them.
> >
> > BUG: kernel NULL pointer dereference, address: 0000000000000012
> > PGD 0 P4D 0
> > Oops: 0000 [#1] SMP PTI
> > CPU: 3 PID: 2210 Comm: modprobe Not tainted
> > 6.1.0-rc1-00171-g2159299a3b74-dirty #217
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
> > RIP: 0010:kprobe_event_gen_test_exit+0x1c/0xb5 [kprobe_event_gen_test]
> > Code: Unable to access opcode bytes at 0xffffffff9ffffff2.
> > RSP: 0018:ffffc900015bfeb8 EFLAGS: 00010246
> > RAX: ffffffffffffffea RBX: ffffffffa0002080 RCX: 0000000000000000
> > RDX: ffffffffa0001054 RSI: ffffffffa0001064 RDI: ffffffffdfc6349c
> > RBP: ffffffffa0000000 R08: 0000000000000004 R09: 00000000001e95c0
> > R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000800
> > R13: ffffffffa0002420 R14: 0000000000000000 R15: 0000000000000000
> > FS:  00007f56b75be540(0000) GS:ffff88813bc00000(0000)
> > knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: ffffffff9ffffff2 CR3: 000000010874a006 CR4: 0000000000330ee0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >   <TASK>
> >   __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
> >
> > Fixes: 64836248dda2 ("tracing: Add kprobe event command generation test module")
>
> Ah, indeed. If anything wrong in the test code and if the
> gen_kprobe_test/gen_kretprobe_test is not initialized, this
> can happen.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
>
> Thank you!
Thanks for the review, will add the Tag in v2.

Thanks,
--
Shang XiaoJing