Re: [BUG] systemd-devd triggers kernel memleak apparently in drivers/core/dd.c: driver_register()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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@linux.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]
> > > 
> > > 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?

> 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?
Or can you test kernel patches to verify the problem is fixed or not if
we send you patches to test?

thanks,

greg k-h