VC4 kernel framework driver - memory leak

[nkichukov]

Hi all,

I have identified a memory leak in the VC4 kernel framework driver implementation on raspberry pi 3b. Details follow below:

kernel: 4.14.0-v7+
compiler: gcc-6.4
raspberry pi running in 32bit mode
OS: Gentoo Linux
Kernel configuration is attached, see below.

Whenever kodi(v17.6) is playing video, I can see that /proc/slabinfo reports number of kmalloc-128 constantly increasing and never releasing:
kmalloc-128 84916 84924 384 21 2 : tunables 0 0 0 : slabdata 4044 4044 0

In about 24 hours this has taken up about 600MB of the memory and the Pi needs to be restarted to avoid swapping. If I stop kodi playback and leave it idle, the kmalloc-128 remains the same until playback is resumed which starts increasing again. If I stop the X server and kodi altogether, the memory is not released.

The memleak pattern is like the one below

(from /sys/kernel/debug/kmemleak):

unreferenced object 0x95ce16c0 (size 128):
comm "kodi.bin", pid 2075, jiffies 891363 (age 2338.023s)
hex dump (first 32 bytes):
01 00 00 00 5c ed 1e 7f 00 00 00 00 00 00 00 00 ...............
d0 16 ce 95 d0 16 ce 95 00 3a fb b4 00 00 00 00 .........:......
backtrace:
[<802827c8>] kmem_cache_alloc_trace+0x234/0x2f8
[<7f1e461c>] vc4_submit_cl_ioctl+0x730/0xb50 [vc4]
[<7f0d796c>] drm_ioctl_kernel+0x78/0xb8 [drm]
[<7f0d7cd4>] drm_ioctl+0x1b4/0x37c [drm]
[<802ac090>] do_vfs_ioctl+0xb0/0x8b4
[<802ac8d8>] SyS_ioctl+0x44/0x6c
[<80108140>] ret_fast_syscall+0x0/0x28
[] 0xffffffff

Let me know if additional information is required to track this issue down.

rpi-4.14.y-kernel_configuration_file.gz

Thank you,
-Nikolay

[pelwell]

It would be best to report this in the VC4 author's repo: https://github.com/anholt/linux/issues

I notice that there is already an issue entitled "vc4: Memory leaks in linux-next-20171110" which looks like it could be a duplicate:

unreferenced object 0xffff800037e03b80 (size 128):