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

[Deucher, Alexander]

[AMD Public Use]

> -----Original Message-----
> From: Holger Kiehl <Holger.Kiehl@xxxxxx>
> Sent: Monday, May 10, 2021 2:21 PM
> To: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx; Pan, Xinhui
> <Xinhui.Pan@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>; Sasha Levin <sashal@xxxxxxxxxx>
> Subject: Re: [PATCH 5.12 195/384] drm/amdgpu: Fix memory leak
> 
> 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.

This patch is a fix specifically for:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f258907fdd835e1aed6d666b00cdd0f186676b7c
It does not make sense on it's own.

Alex