Re: [Bug report] Memory leak in scmi_device_create

[Alice Ryhl]

On Wed, Mar 05, 2025 at 05:10:16PM +0000, Cristian Marussi wrote:
> On Wed, Mar 05, 2025 at 11:59:58AM +0000, Alice Ryhl wrote:
> > Dear SYSTEM CONTROL & POWER/MANAGEMENT INTERFACE (SCPI/SCMI) Message
> > Protocol drivers maintainers,
> > 
> > I flashed a v6.13-rc3 kernel onto a Rock5B board and noticed the
> > following output in my terminal:
> > 
> > [  687.694465] kmemleak: 4 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
> > 
> > It seems that there is a memory leak for devices created with
> > scmi_device_create.
> > 
> `
> Hi Alice,
> 
> thanks for this report.
> 
> > This was with a kernel running v6.13-rc3, but as far as I can tell, no
> > relevant changes have landed since v6.13-rc3. My tree *does* include
> > commit 295416091e44 ("firmware: arm_scmi: Fix slab-use-after-free in
> > scmi_bus_notifier()"). I've only seen this kmemleak report once, so it's
> > not happening consistently.
> > 
> > See below for the full kmemleak report.
> > 
> > Alice
> > 
> > $ sudo cat /sys/kernel/debug/kmemleak
> > unreferenced object 0xffffff8106c86000 (size 2048):
> >   comm "swapper/0", pid 1, jiffies 4294893094
> >   hex dump (first 32 bytes):
> >     02 00 00 00 10 00 00 00 c0 01 bc 03 81 ff ff ff  ................
> >     60 67 ba 03 81 ff ff ff 18 60 c8 06 81 ff ff ff  `g.......`......
> >   backtrace (crc feae9680):
> >     [<00000000197aa008>] kmemleak_alloc+0x34/0xa0
> >     [<0000000056fe02c9>] __kmalloc_cache_noprof+0x1e0/0x450
> >     [<00000000a8b3dfe1>] __scmi_device_create+0xb4/0x2b4
> >     [<000000008714917b>] scmi_device_create+0x40/0x194
> >     [<000000001818f3cf>] scmi_chan_setup+0x144/0x3b8
> >     [<00000000970bad38>] scmi_probe+0x584/0xa78
> >     [<000000002600d2fd>] platform_probe+0xbc/0xf0
> >     [<00000000f6f556b4>] really_probe+0x1b8/0x520
> >     [<00000000eed93d59>] __driver_probe_device+0xe0/0x1d8
> >     [<00000000d613b754>] driver_probe_device+0x6c/0x208
> >     [<00000000187a9170>] __driver_attach+0x168/0x328
> >     [<00000000e3ff1834>] bus_for_each_dev+0x14c/0x178
> >     [<00000000984a3176>] driver_attach+0x34/0x44
> >     [<00000000fc35bf2a>] bus_add_driver+0x1bc/0x358
> >     [<00000000747fce19>] driver_register+0xc0/0x1a0
> >     [<0000000081cb8754>] __platform_driver_register+0x40/0x50
> > unreferenced object 0xffffff8103bc01c0 (size 32):
> 
> I could not reproduce on my setup, even though I run a system with
> all the existent SCMI protocols (and related drivers) enabled (and
> so a lot of device creations) and a downstream test driver that causes
> even more SCMI devices to be created/destroyed at load/unload.
> 
> Coming down the path from scmi_chan_setup(), it seems something around
> transport devices creation, but it is not obvious to me where the leak
> could hide....
> 
> ...any particular setup on your side ? ...using LKMs, loading/unloading,
> any usage pattern that could help me reproduce ?

I looked into this a bit more, and actually it does happen consistently.
It's just that kmemleak doesn't report it until 10 minutes after
booting, so I did not notice it.

As for my setup, well, I boot the kernel over pxe and the rootfs is
mounted over NFSv4. The memory leak happens even if I don't do anything
at all - I just boot and wait. The device is a Radxa Rock5B.

Not sure what other information there is to give.

I tried again with v6.14-rc5, and I still got the leak:

user@rk3588-ci:~$ sudo cat /sys/kernel/debug/kmemleak
unreferenced object 0xffffff81068c0000 (size 2048):
  comm "swapper/0", pid 1, jiffies 4294893128
  hex dump (first 32 bytes):
    02 00 00 00 10 00 00 00 40 a3 7a 03 81 ff ff ff  ........@.z.....
    60 c8 79 03 81 ff ff ff 18 00 8c 06 81 ff ff ff  `.y.............
  backtrace (crc 60df30fb):
    kmemleak_alloc+0x34/0xa0
    __kmalloc_cache_noprof+0x1e0/0x450
    __scmi_device_create+0xb4/0x2b4
    scmi_device_create+0x40/0x194
    scmi_chan_setup+0x144/0x3b8
    scmi_probe+0x51c/0x9fc
    platform_probe+0xbc/0xf0
    really_probe+0x1b8/0x520
    __driver_probe_device+0xe0/0x1d8
    driver_probe_device+0x6c/0x208
    __driver_attach+0x168/0x328
    bus_for_each_dev+0x14c/0x178
    driver_attach+0x34/0x44
    bus_add_driver+0x1bc/0x358
    driver_register+0xc0/0x1a0
    __platform_driver_register+0x40/0x50
unreferenced object 0xffffff81037aa340 (size 32):
  comm "swapper/0", pid 1, jiffies 4294893128
  hex dump (first 32 bytes):
    5f 5f 73 63 6d 69 5f 74 72 61 6e 73 70 6f 72 74  __scmi_transport
    5f 64 65 76 69 63 65 5f 72 78 5f 31 30 00 ff ff  _device_rx_10...
  backtrace (crc 8dab7ca7):
    kmemleak_alloc+0x34/0xa0
    __kmalloc_node_track_caller_noprof+0x234/0x528
    kstrdup+0x48/0x80
    kstrdup_const+0x30/0x3c
    __scmi_device_create+0xd4/0x2b4
    scmi_device_create+0x40/0x194
    scmi_chan_setup+0x144/0x3b8
    scmi_probe+0x51c/0x9fc
    platform_probe+0xbc/0xf0
    really_probe+0x1b8/0x520
    __driver_probe_device+0xe0/0x1d8
    driver_probe_device+0x6c/0x208
    __driver_attach+0x168/0x328
    bus_for_each_dev+0x14c/0x178
    driver_attach+0x34/0x44
    bus_add_driver+0x1bc/0x358
unreferenced object 0xffffff810379c860 (size 16):
  comm "swapper/0", pid 1, jiffies 4294893128
  hex dump (first 16 bytes):
    73 63 6d 69 5f 64 65 76 2e 32 00 03 81 ff ff ff  scmi_dev.2......
  backtrace (crc ccc21b9a):
    kmemleak_alloc+0x34/0xa0
    __kmalloc_node_track_caller_noprof+0x234/0x528
    kvasprintf+0x90/0x11c
    kvasprintf_const+0x98/0x138
    kobject_set_name_vargs+0x68/0x104
    dev_set_name+0x6c/0x98
    __scmi_device_create+0x17c/0x2b4
    scmi_device_create+0x40/0x194
    scmi_chan_setup+0x144/0x3b8
    scmi_probe+0x51c/0x9fc
    platform_probe+0xbc/0xf0
    really_probe+0x1b8/0x520
    __driver_probe_device+0xe0/0x1d8
    driver_probe_device+0x6c/0x208
    __driver_attach+0x168/0x328
    bus_for_each_dev+0x14c/0x178
unreferenced object 0xffffff8105be7400 (size 512):
  comm "swapper/0", pid 1, jiffies 4294893128
  hex dump (first 32 bytes):
    00 00 00 00 ad 4e ad de ff ff ff ff 00 00 00 00  .....N..........
    ff ff ff ff ff ff ff ff c0 b4 f0 83 c0 ff ff ff  ................
  backtrace (crc 7b92a969):
    kmemleak_alloc+0x34/0xa0
    __kmalloc_cache_noprof+0x1e0/0x450
    device_add+0x54/0x570
    device_register+0x20/0x30
    __scmi_device_create+0x184/0x2b4
    scmi_device_create+0x40/0x194
    scmi_chan_setup+0x144/0x3b8
    scmi_probe+0x51c/0x9fc
    platform_probe+0xbc/0xf0
    really_probe+0x1b8/0x520
    __driver_probe_device+0xe0/0x1d8
    driver_probe_device+0x6c/0x208
    __driver_attach+0x168/0x328
    bus_for_each_dev+0x14c/0x178
    driver_attach+0x34/0x44
    bus_add_driver+0x1bc/0x358