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Message-Id: <20221107223835.4d5583852a7efef1a2ac19af@kernel.org>
Date: Mon, 7 Nov 2022 22:38:35 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Shang XiaoJing <shangxiaojing@...wei.com>
Cc: <rostedt@...dmis.org>, <zanussi@...nel.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] tracing: kprobe: Fix potential null-ptr-deref on
trace_array in kprobe_event_gen_test_exit()
Hi,
On Mon, 7 Nov 2022 15:16:17 +0800
Shang XiaoJing <shangxiaojing@...wei.com> 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@...wei.com>
> ---
> 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.
> 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.
Thank you,
> goto out;
> }
>
> @@ -222,9 +226,10 @@ static int __init kprobe_event_gen_test_init(void)
> ret = test_gen_kretprobe_cmd();
> if (ret) {
> if (trace_event_file_is_valid(gen_kretprobe_test)) {
> - WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
> - "kprobes",
> - "gen_kretprobe_test", false));
> + if (gen_kretprobe_test->tr)
> + WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
> + "kprobes",
> + "gen_kretprobe_test", false));
> trace_put_event_file(gen_kretprobe_test);
> }
> WARN_ON(kprobe_event_delete("gen_kretprobe_test"));
> @@ -236,10 +241,11 @@ static int __init kprobe_event_gen_test_init(void)
> static void __exit kprobe_event_gen_test_exit(void)
> {
> if (trace_event_file_is_valid(gen_kprobe_test)) {
> - /* Disable the event or you can't remove it */
> - WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,
> - "kprobes",
> - "gen_kprobe_test", false));
> + if (gen_kprobe_test->tr)
> + /* Disable the event or you can't remove it */
> + WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,
> + "kprobes",
> + "gen_kprobe_test", false));
>
> /* Now give the file and instance back */
> trace_put_event_file(gen_kprobe_test);
> @@ -250,10 +256,11 @@ static void __exit kprobe_event_gen_test_exit(void)
> WARN_ON(kprobe_event_delete("gen_kprobe_test"));
>
> if (trace_event_file_is_valid(gen_kretprobe_test)) {
> - /* Disable the event or you can't remove it */
> - WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
> - "kprobes",
> - "gen_kretprobe_test", false));
> + if (gen_kretprobe_test->tr)
> + /* Disable the event or you can't remove it */
> + WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
> + "kprobes",
> + "gen_kretprobe_test", false));
>
> /* Now give the file and instance back */
> trace_put_event_file(gen_kretprobe_test);
> --
> 2.17.1
>
--
Masami Hiramatsu (Google) <mhiramat@...nel.org>
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