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Date: Tue, 28 Mar 2023 21:06:24 +0200
From: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
To: Armin Wolf <W_Armin@....de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
linux-kernel@...r.kernel.org, Hans de Goede <hdegoede@...hat.com>,
Mark Gross <markgross@...nel.org>,
platform-driver-x86@...r.kernel.org
Subject: Re: [BUG] systemd-devd triggers kernel memleak apparently in
drivers/core/dd.c: driver_register()
On 3/28/2023 6:53 PM, Armin Wolf wrote:
> Am 28.03.23 um 14:44 schrieb Mirsad Todorovac:
>
>> On 3/28/23 14:17, Greg Kroah-Hartman wrote:
>>> On Tue, Mar 28, 2023 at 02:08:06PM +0200, Mirsad Todorovac wrote:
>>>> On 3/28/23 13:59, Mirsad Todorovac wrote:
>>>>
>>>>> On 3/28/23 13:28, Greg Kroah-Hartman wrote:
>>>>>> On Tue, Mar 28, 2023 at 01:13:33PM +0200, Mirsad Todorovac wrote:
>>>>>>> Hi all,
>>>>>>>
>>>>>>> Here is another kernel memory leak report, just as I thought we have done with
>>>>>>> them by the xhci patch by Mathias.
>>>>>>>
>>>>>>> The memory leaks were caught on an AlmaLinux 8.7 (CentOS) fork system, running
>>>>>>> on a Lenovo desktop box (see lshw.txt) and the newest Linux kernel 6.3-rc4 commit
>>>>>>> g3a93e40326c8 with Mathias' patch for a xhci systemd-devd triggered leak.
>>>>>>>
>>>>>>> See: <20230327095019.1017159-1-mathias.nyman@...ux.intel.com> on LKML.
>>>>>>>
>>>>>>> This leak is also systemd-devd triggered, except for the memstick_check() leaks
>>>>>>> which I was unable to bisect due to the box not booting older kernels (work in
>>>>>>> progress).
>>>>>>>
>>>>>>> unreferenced object 0xffff88ad12392710 (size 96):
>>>>>>> comm "systemd-udevd", pid 735, jiffies 4294896759 (age 2257.568s)
>>>>>>> hex dump (first 32 bytes):
>>>>>>> 53 65 72 69 61 6c 50 6f 72 74 31 41 64 64 72 65 SerialPort1Addre
>>>>>>> 73 73 2c 33 46 38 2f 49 52 51 34 3b 5b 4f 70 74 ss,3F8/IRQ4;[Opt
>>>>>>> backtrace:
>>>>>>> [<ffffffffae8fb26c>] slab_post_alloc_hook+0x8c/0x3e0
>>>>>>> [<ffffffffae902b49>] __kmem_cache_alloc_node+0x1d9/0x2a0
>>>>>>> [<ffffffffae8773c9>] __kmalloc_node_track_caller+0x59/0x180
>>>>>>> [<ffffffffae866a1a>] kstrdup+0x3a/0x70
>>>>>>> [<ffffffffc0d839aa>] tlmi_extract_output_string.isra.0+0x2a/0x60 [think_lmi]
>>>>>>> [<ffffffffc0d83b64>] tlmi_setting.constprop.4+0x54/0x90 [think_lmi]
>>>>>>> [<ffffffffc0d842b1>] tlmi_probe+0x591/0xba0 [think_lmi]
>>>>>>> [<ffffffffc051dc53>] wmi_dev_probe+0x163/0x230 [wmi]
>>>>>>
> Hi,
>
> this "SerialPort1Address" string looks like a BIOS setup option, and indeed think_lmi allows for
> changing BIOS setup options over sysfs. While looking at current_value_show() in think-lmi.c, i noticed
> that "item" holds a string which is allocated with kstrdup(), so it has to be freed using kfree().
> This however does not happen if strbrk() fails, so maybe the memory leak is caused by this?
>
> Armin Wolf
Hi Armin,
I tried your suggestion, and though it is an obvious improvement and a leak fix, this
was not the one we were searching for.
I tested the following patch:
diff --git a/drivers/platform/x86/think-lmi.c b/drivers/platform/x86/think-lmi.c
index c816646eb661..1e77ecb0cba8 100644
--- a/drivers/platform/x86/think-lmi.c
+++ b/drivers/platform/x86/think-lmi.c
@@ -929,8 +929,10 @@ static ssize_t current_value_show(struct kobject *kobj, struct kobj_attribute *a
/* validate and split from `item,value` -> `value` */
value = strpbrk(item, ",");
- if (!value || value == item || !strlen(value + 1))
+ if (!value || value == item || !strlen(value + 1)) {
+ kfree(item);
return -EINVAL;
+ }
ret = sysfs_emit(buf, "%s\n", value + 1);
kfree(item);
(I would also object to the use of strlen() here, for it is inherently insecure
against SEGFAULT in kernel space.)
I still get:
[root@...mtodorov marvin]# uname -rms
Linux 6.3.0-rc4-armin-patch-00025-g3a93e40326c8-dirty x86_64
[root@...mtodorov marvin]# cat /sys/kernel/debug/kmemleak [edited]
unreferenced object 0xffff8eb008ef9260 (size 96):
comm "systemd-udevd", pid 771, jiffies 4294896499 (age 74.880s)
hex dump (first 32 bytes):
53 65 72 69 61 6c 50 6f 72 74 31 41 64 64 72 65 SerialPort1Addre
73 73 2c 33 46 38 2f 49 52 51 34 3b 5b 4f 70 74 ss,3F8/IRQ4;[Opt
backtrace:
[<ffffffff9eafb26c>] slab_post_alloc_hook+0x8c/0x3e0
[<ffffffff9eb02b49>] __kmem_cache_alloc_node+0x1d9/0x2a0
[<ffffffff9ea773c9>] __kmalloc_node_track_caller+0x59/0x180
[<ffffffff9ea66a1a>] kstrdup+0x3a/0x70
[<ffffffffc0eef9aa>] tlmi_extract_output_string.isra.0+0x2a/0x60 [think_lmi]
[<ffffffffc0eefb64>] tlmi_setting.constprop.4+0x54/0x90 [think_lmi]
[<ffffffffc0ef02c1>] tlmi_probe+0x591/0xba0 [think_lmi]
[<ffffffffc0629c53>] wmi_dev_probe+0x163/0x230 [wmi]
[<ffffffff9f1987eb>] really_probe+0x17b/0x3d0
[<ffffffff9f198ad4>] __driver_probe_device+0x84/0x190
[<ffffffff9f198c14>] driver_probe_device+0x24/0xc0
[<ffffffff9f198ed2>] __driver_attach+0xc2/0x190
[<ffffffff9f195ab1>] bus_for_each_dev+0x81/0xd0
[<ffffffff9f197c62>] driver_attach+0x22/0x30
[<ffffffff9f197354>] bus_add_driver+0x1b4/0x240
[<ffffffff9f19a0a2>] driver_register+0x62/0x120
unreferenced object 0xffff8eb018ddbb40 (size 64):
comm "systemd-udevd", pid 771, jiffies 4294896528 (age 74.780s)
hex dump (first 32 bytes):
55 53 42 50 6f 72 74 41 63 63 65 73 73 2c 45 6e USBPortAccess,En
61 62 6c 65 64 3b 5b 4f 70 74 69 6f 6e 61 6c 3a abled;[Optional:
backtrace:
[<ffffffff9eafb26c>] slab_post_alloc_hook+0x8c/0x3e0
[<ffffffff9eb02b49>] __kmem_cache_alloc_node+0x1d9/0x2a0
[<ffffffff9ea773c9>] __kmalloc_node_track_caller+0x59/0x180
[<ffffffff9ea66a1a>] kstrdup+0x3a/0x70
[<ffffffffc0eef9aa>] tlmi_extract_output_string.isra.0+0x2a/0x60 [think_lmi]
[<ffffffffc0eefb64>] tlmi_setting.constprop.4+0x54/0x90 [think_lmi]
[<ffffffffc0ef02c1>] tlmi_probe+0x591/0xba0 [think_lmi]
[<ffffffffc0629c53>] wmi_dev_probe+0x163/0x230 [wmi]
[<ffffffff9f1987eb>] really_probe+0x17b/0x3d0
[<ffffffff9f198ad4>] __driver_probe_device+0x84/0x190
[<ffffffff9f198c14>] driver_probe_device+0x24/0xc0
[<ffffffff9f198ed2>] __driver_attach+0xc2/0x190
[<ffffffff9f195ab1>] bus_for_each_dev+0x81/0xd0
[<ffffffff9f197c62>] driver_attach+0x22/0x30
[<ffffffff9f197354>] bus_add_driver+0x1b4/0x240
[<ffffffff9f19a0a2>] driver_register+0x62/0x120
unreferenced object 0xffff8eb006fe2b40 (size 64):
comm "systemd-udevd", pid 771, jiffies 4294896542 (age 74.724s)
hex dump (first 32 bytes):
55 53 42 42 49 4f 53 53 75 70 70 6f 72 74 2c 45 USBBIOSSupport,E
6e 61 62 6c 65 64 3b 5b 4f 70 74 69 6f 6e 61 6c nabled;[Optional
backtrace:
[<ffffffff9eafb26c>] slab_post_alloc_hook+0x8c/0x3e0
[<ffffffff9eb02b49>] __kmem_cache_alloc_node+0x1d9/0x2a0
[<ffffffff9ea773c9>] __kmalloc_node_track_caller+0x59/0x180
[<ffffffff9ea66a1a>] kstrdup+0x3a/0x70
[<ffffffffc0eef9aa>] tlmi_extract_output_string.isra.0+0x2a/0x60 [think_lmi]
[<ffffffffc0eefb64>] tlmi_setting.constprop.4+0x54/0x90 [think_lmi]
[<ffffffffc0ef02c1>] tlmi_probe+0x591/0xba0 [think_lmi]
[<ffffffffc0629c53>] wmi_dev_probe+0x163/0x230 [wmi]
[<ffffffff9f1987eb>] really_probe+0x17b/0x3d0
[<ffffffff9f198ad4>] __driver_probe_device+0x84/0x190
[<ffffffff9f198c14>] driver_probe_device+0x24/0xc0
[<ffffffff9f198ed2>] __driver_attach+0xc2/0x190
[<ffffffff9f195ab1>] bus_for_each_dev+0x81/0xd0
[<ffffffff9f197c62>] driver_attach+0x22/0x30
[<ffffffff9f197354>] bus_add_driver+0x1b4/0x240
[<ffffffff9f19a0a2>] driver_register+0x62/0x120
There are currently 84 wmi_dev_probe leaks, sized mostly 64 bytes, and one 96 and two 192 bytes.
I also cannot figure out the mechanism by which current_value_show() is called, when it is static?
Any idea?
Thanks.
Best regards,
Mirsad
>>>>>> Why aren't you looking at the wmi.c driver? That should be where the
>>>>>> issue is, not the driver core, right?
>>>>>>
>>>>>> thanks,
>>>>>>
>>>>>> greg k-h
>>>>>
>>>>> Hi, Mr. Greg,
>>>>>
>>>>> Thanks for the quick reply.
>>>>>
>>>>> I have added CC: for additional developers per drivers/platform/x86/wmi.c,
>>>>> however, this seems to me like hieroglyphs. There is nothing obvious, but
>>>>> I had not noticed it with v6.3-rc3?
>>>>>
>>>>> Maybe, there seems to be something off:
>>>>>
>>>>> 949 static int wmi_dev_probe(struct device *dev)
>>>>> 950 {
>>>>> 951 struct wmi_block *wblock = dev_to_wblock(dev);
>>>>> 952 struct wmi_driver *wdriver = drv_to_wdrv(dev->driver);
>>>>> 953 int ret = 0;
>>>>> 954 char *buf;
>>>>> 955
>>>>> 956 if (ACPI_FAILURE(wmi_method_enable(wblock, true)))
>>>>> 957 dev_warn(dev, "failed to enable device -- probing anyway\n");
>>>>> 958
>>>>> 959 if (wdriver->probe) {
>>>>> 960 ret = wdriver->probe(dev_to_wdev(dev),
>>>>> 961 find_guid_context(wblock, wdriver));
>>>>> 962 if (ret != 0)
>>>>> 963 goto probe_failure;
>>>>> 964 }
>>>>> 965
>>>>> 966 /* driver wants a character device made */
>>>>> 967 if (wdriver->filter_callback) {
>>>>> 968 /* check that required buffer size declared by driver or MOF */
>>>>> 969 if (!wblock->req_buf_size) {
>>>>> 970 dev_err(&wblock->dev.dev,
>>>>> 971 "Required buffer size not set\n");
>>>>> 972 ret = -EINVAL;
>>>>> 973 goto probe_failure;
>>>>> 974 }
>>>>> 975
>>>>> 976 wblock->handler_data = kmalloc(wblock->req_buf_size,
>>>>> 977 GFP_KERNEL);
>>>>> 978 if (!wblock->handler_data) {
>>>>> 979 ret = -ENOMEM;
>>>>> 980 goto probe_failure;
>>>>> 981 }
>>>>> 982
>>>>> 983 buf = kasprintf(GFP_KERNEL, "wmi/%s", wdriver->driver.name);
>>>>> 984 if (!buf) {
>>>>> 985 ret = -ENOMEM;
>>>>> 986 goto probe_string_failure;
>>>>> 987 }
>>>>> 988 wblock->char_dev.minor = MISC_DYNAMIC_MINOR;
>>>>> 989 wblock->char_dev.name = buf;
>>>>> 990 wblock->char_dev.fops = &wmi_fops;
>>>>> 991 wblock->char_dev.mode = 0444;
>>>>> 992 ret = misc_register(&wblock->char_dev);
>>>>> 993 if (ret) {
>>>>> 994 dev_warn(dev, "failed to register char dev: %d\n", ret);
>>>>> 995 ret = -ENOMEM;
>>>>> 996 goto probe_misc_failure;
>>>>> 997 }
>>>>> 998 }
>>>>> 999
>>>>> 1000 set_bit(WMI_PROBED, &wblock->flags);
>>>>> 1001 return 0;
>>>>> 1002
>>>>> 1003 probe_misc_failure:
>>>>> 1004 kfree(buf);
>>>>> 1005 probe_string_failure:
>>>>> 1006 kfree(wblock->handler_data);
>>>>> 1007 probe_failure:
>>>>> 1008 if (ACPI_FAILURE(wmi_method_enable(wblock, false)))
>>>>> 1009 dev_warn(dev, "failed to disable device\n");
>>>>>
>>>>>
>>>>> char *buf is passed to kfree(buf) uninitialised if wdriver->filter_callback
>>>>> is not set.
>>>>>
>>>>> It seems like a logical error per se, but I don't believe this is the cause
>>>>> of the leak?
>>>>
>>>> CORRECTION:
>>>>
>>>> I overlooked the "return 0" in line 1001.
>>>
>>> Yeah, and the memory looks to be freed properly in the wmi_dev_remove()
>>> callback, right?
>>
>> It would appear so. To verify that:
>>
>> Alloc:
>> 976 wblock->handler_data = kmalloc(wblock->req_buf_size,
>> GFP_KERNEL);
>> <check>
>>
>> 983 buf = kasprintf(GFP_KERNEL, "wmi/%s", wdriver->driver.name);
>> <check>
>> 989 wblock->char_dev.name = buf;
>>
>> In lines 1022-1023:
>>
>> 1022 kfree(wblock->char_dev.name);
>> 1023 kfree(wblock->handler_data);
>>
>>>> This is why I don't think things should be rushed, but analysed with clear and
>>>> cold head. And with as many eyes as possible :)
>>>>
>>>> The driver stuff is my long-term research interest. To state the obvious,
>>>> the printing and multimedia education and industry in general would benefit from
>>>> the open-source drivers for many instruments that still work, but are obsoleted
>>>> by the producer and require unsupported versions of the OS.
>>>>
>>>> Thank you again for reviewing the bug report, however, ATM I do not think I have
>>>> what it takes to hunt down the memleak. :-/
>>>
>>> Do you have a reproducer that you can use to show the problem better?
>>
>> Unfortunately, the problem doesn't seem to appear during the run of a particular
>> test, but immediately on startup of the OS. This makes it awkward to pinpoint the
>> exact service that triggered memory leaks. But they would appear to have to do
>> with the initialisation of the USB devices, wouldn't they?
>>
>> There seem to be strings:
>>
>> "USBPortAccess,Enabled;[Optional:"
>> "USBBIOSSupport,Enabled;[Optional"
>> "USBEnumerationDelay,Disabled;[Op"
>>
>> This seems to be happening during USB initialisation and before any services.
>> But I might as well be wrong.
>>
>>> Or can you test kernel patches to verify the problem is fixed or not if
>>> we send you patches to test?
>>
>> Certainly, Lord willing, I can test the patches in the same environment that
>> mainfeted the bug (or memleak).
>>
>> Best regards,
>> Mirsad
>>
--
Mirsad Todorovac
Sistem inženjer
Grafički fakultet | Akademija likovnih umjetnosti
Sveučilište u Zagrebu
System engineer
Faculty of Graphic Arts | Academy of Fine Arts
University of Zagreb, Republic of Croatia
tel. +385 (0)1 3711 451
mob. +385 91 57 88 355
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