Re: [PATCH 5.12 195/384] drm/amdgpu: Fix memory leak

From: Holger Kiehl
Date: Mon May 10 2021 - 14:26:45 EST

On Mon, 10 May 2021, Greg Kroah-Hartman wrote:

> From: xinhui pan <xinhui.pan@xxxxxxx>
>
> [ Upstream commit 79fcd446e7e182c52c2c808c76f8de3eb6714349 ]
>
> drm_gem_object_put() should be paired with drm_gem_object_lookup().
>
> All gem objs are saved in fb->base.obj[]. Need put the old first before
> assign a new obj.
>
> Trigger VRAM leak by running command below
> $ service gdm restart
>
> Signed-off-by: xinhui pan <xinhui.pan@xxxxxxx>
> Acked-by: Alex Deucher <alexander.deucher@xxxxxxx>
> Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_display.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> index f753e04fee99..cbe050436c7b 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> @@ -910,8 +910,9 @@ int amdgpu_display_framebuffer_init(struct drm_device *dev,
> }
>
> for (i = 1; i < rfb->base.format->num_planes; ++i) {
> + drm_gem_object_get(rfb->base.obj[0]);
> + drm_gem_object_put(rfb->base.obj[i]);
> rfb->base.obj[i] = rfb->base.obj[0];
> - drm_gem_object_get(rfb->base.obj[i]);
> }
>
> return 0;
> @@ -960,6 +961,7 @@ amdgpu_display_user_framebuffer_create(struct drm_device *dev,
> return ERR_PTR(ret);
> }
>
> + drm_gem_object_put(obj);
> return &amdgpu_fb->base;
> }
>
> --
> 2.30.2
>
This causes the following error on a AMD APU Ryzen 7 4750G:

May 10 19:29:50 bb8 kernel: [ 2.730473] [drm] Initialized amdgpu 3.40.0 20150101 for 0000:04:00.0 on minor 0
May 10 19:29:50 bb8 kernel: [ 2.748000] ------------[ cut here ]------------
May 10 19:29:50 bb8 kernel: [ 2.748003] refcount_t: underflow; use-after-free.
May 10 19:29:50 bb8 kernel: [ 2.748008] WARNING: CPU: 10 PID: 513 at lib/refcount.c:28 refcount_warn_saturate+0xa6/0xf0
May 10 19:29:50 bb8 kernel: [ 2.748014] Modules linked in: amdgpu raid1 raid0 md_mod drm_ttm_helper ttm mfd_core iommu_v2 gpu_sched i2c_algo_bit crct10dif_pclmul crc32_pclmul crc32c_intel drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops cec ghash_clmulni_intel drm r8169 ccp realtek pinctrl_amd fuse ecryptfs
May 10 19:29:50 bb8 kernel: [ 2.748029] CPU: 10 PID: 513 Comm: plymouthd Not tainted 5.12.3 #1
May 10 19:29:50 bb8 kernel: [ 2.748031] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./X300M-STX, BIOS P1.60 04/29/2021
May 10 19:29:50 bb8 kernel: [ 2.748032] RIP: 0010:refcount_warn_saturate+0xa6/0xf0
May 10 19:29:50 bb8 kernel: [ 2.748034] Code: 05 79 34 17 01 01 e8 cd 51 4a 00 0f 0b c3 80 3d 67 34 17 01 00 75 95 48 c7 c7 a0 90 13 99 c6 05 57 34 17 01 01 e8 ae 51 4a 00 <0f> 0b c3 80 3d 46 34 17 01 00 0f 85 72 ff ff ff 48 c7 c7 f8 90 13
May 10 19:29:50 bb8 kernel: [ 2.748036] RSP: 0018:ffffb2ccc07f7d58 EFLAGS: 00010292
May 10 19:29:50 bb8 kernel: [ 2.748038] RAX: 0000000000000026 RBX: ffff90d28d313000 RCX: 0000000000000027
May 10 19:29:50 bb8 kernel: [ 2.748039] RDX: ffff90e081c975c8 RSI: 0000000000000001 RDI: ffff90e081c975c0
May 10 19:29:50 bb8 kernel: [ 2.748040] RBP: ffff90d290b1b458 R08: 0000000000000000 R09: ffffb2ccc07f7b98
May 10 19:29:50 bb8 kernel: [ 2.748040] R10: 0000000000000001 R11: 0000000000000001 R12: ffff90d28d313000
May 10 19:29:50 bb8 kernel: [ 2.748041] R13: ffff90d28d313128 R14: ffff90d28d313050 R15: ffff90d28d313000
May 10 19:29:50 bb8 kernel: [ 2.748042] FS: 00007fa31f454800(0000) GS:ffff90e081c80000(0000) knlGS:0000000000000000
May 10 19:29:50 bb8 kernel: [ 2.748043] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
May 10 19:29:50 bb8 kernel: [ 2.748044] CR2: 00007fa31f42e000 CR3: 000000010e1d2000 CR4: 0000000000350ee0
May 10 19:29:50 bb8 kernel: [ 2.748046] Call Trace:
May 10 19:29:50 bb8 kernel: [ 2.748049] drm_gem_object_release_handle+0x6b/0x80 [drm]
May 10 19:29:50 bb8 kernel: [ 2.748068] ? drm_mode_destroy_dumb+0x40/0x40 [drm]
May 10 19:29:50 bb8 kernel: [ 2.748086] drm_gem_handle_delete+0x4f/0x80 [drm]
May 10 19:29:50 bb8 kernel: [ 2.748101] ? drm_mode_destroy_dumb+0x40/0x40 [drm]
May 10 19:29:50 bb8 kernel: [ 2.748117] drm_ioctl_kernel+0x87/0xd0 [drm]
May 10 19:29:50 bb8 kernel: [ 2.748133] drm_ioctl+0x205/0x3a0 [drm]
May 10 19:29:50 bb8 kernel: [ 2.748149] ? drm_mode_destroy_dumb+0x40/0x40 [drm]
May 10 19:29:50 bb8 kernel: [ 2.748164] amdgpu_drm_ioctl+0x49/0x80 [amdgpu]
May 10 19:29:50 bb8 kernel: [ 2.748263] __x64_sys_ioctl+0x82/0xb0
May 10 19:29:50 bb8 kernel: [ 2.748266] do_syscall_64+0x33/0x40
May 10 19:29:50 bb8 kernel: [ 2.748269] entry_SYSCALL_64_after_hwframe+0x44/0xae
May 10 19:29:50 bb8 kernel: [ 2.748271] RIP: 0033:0x7fa31f7d30ab
May 10 19:29:50 bb8 kernel: [ 2.748273] Code: ff ff ff 85 c0 79 9b 49 c7 c4 ff ff ff ff 5b 5d 4c 89 e0 41 5c c3 66 0f 1f 84 00 00 00 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 95 bd 0c 00 f7 d8 64 89 01 48
May 10 19:29:50 bb8 kernel: [ 2.748274] RSP: 002b:00007ffe145fb638 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
May 10 19:29:50 bb8 kernel: [ 2.748275] RAX: ffffffffffffffda RBX: 00007ffe145fb67c RCX: 00007fa31f7d30ab
May 10 19:29:50 bb8 kernel: [ 2.748276] RDX: 00007ffe145fb67c RSI: 00000000c00464b4 RDI: 000000000000000a
May 10 19:29:50 bb8 kernel: [ 2.748277] RBP: 00000000c00464b4 R08: 00005620f7832c40 R09: 0000000000000007
May 10 19:29:50 bb8 kernel: [ 2.748278] R10: 00005620f7832c40 R11: 0000000000000246 R12: 0000000000000001
May 10 19:29:50 bb8 kernel: [ 2.748278] R13: 000000000000000a R14: 000000000000000b R15: 00007fa31f8c6e20
May 10 19:29:50 bb8 kernel: [ 2.748280] ---[ end trace 57825da3e46ebfc7 ]---

On another system with a Ryzen 5 3400G a reboot will hang.

If I remove this patch the system boots fine and there is no error
message.

Regards,
Holger