Re: [PATCH v2 3/3] drm/meson: remove drm bridges at aggregate driver unbind time

[Neil Armstrong <neil.armstrong@linaro.org>]

On 21/09/2022 00:28, Adrián Larumbe wrote:
> drm bridges added by meson_encoder_hdmi_init and meson_encoder_cvbs_init
> were not manually removed at module unload time, which caused dangling
> references to freed memory to remain linked in the global bridge_list.
> 
> When loading the driver modules back in, the same functions would again
> call drm_bridge_add, and when traversing the global bridge_list, would
> end up peeking into freed memory.
> 
> Once again KASAN revealed the problem:
> 
> [  +0.000095] =============================================================
> [  +0.000008] BUG: KASAN: use-after-free in __list_add_valid+0x9c/0x120
> [  +0.000018] Read of size 8 at addr ffff00003da291f0 by task modprobe/2483
> 
> [  +0.000018] CPU: 3 PID: 2483 Comm: modprobe Tainted: G         C O      5.19.0-rc6-lrmbkasan+ #1
> [  +0.000011] Hardware name: Hardkernel ODROID-N2Plus (DT)
> [  +0.000008] Call trace:
> [  +0.000006]  dump_backtrace+0x1ec/0x280
> [  +0.000012]  show_stack+0x24/0x80
> [  +0.000008]  dump_stack_lvl+0x98/0xd4
> [  +0.000011]  print_address_description.constprop.0+0x80/0x520
> [  +0.000011]  print_report+0x128/0x260
> [  +0.000008]  kasan_report+0xb8/0xfc
> [  +0.000008]  __asan_report_load8_noabort+0x3c/0x50
> [  +0.000009]  __list_add_valid+0x9c/0x120
> [  +0.000009]  drm_bridge_add+0x6c/0x104 [drm]
> [  +0.000165]  dw_hdmi_probe+0x1900/0x2360 [dw_hdmi]
> [  +0.000022]  meson_dw_hdmi_bind+0x520/0x814 [meson_dw_hdmi]
> [  +0.000014]  component_bind+0x174/0x520
> [  +0.000012]  component_bind_all+0x1a8/0x38c
> [  +0.000010]  meson_drv_bind_master+0x5e8/0xb74 [meson_drm]
> [  +0.000032]  meson_drv_bind+0x20/0x2c [meson_drm]
> [  +0.000027]  try_to_bring_up_aggregate_device+0x19c/0x390
> [  +0.000010]  component_master_add_with_match+0x1c8/0x284
> [  +0.000009]  meson_drv_probe+0x274/0x280 [meson_drm]
> [  +0.000026]  platform_probe+0xd0/0x220
> [  +0.000009]  really_probe+0x3ac/0xa80
> [  +0.000009]  __driver_probe_device+0x1f8/0x400
> [  +0.000009]  driver_probe_device+0x68/0x1b0
> [  +0.000009]  __driver_attach+0x20c/0x480
> [  +0.000008]  bus_for_each_dev+0x114/0x1b0
> [  +0.000009]  driver_attach+0x48/0x64
> [  +0.000008]  bus_add_driver+0x390/0x564
> [  +0.000009]  driver_register+0x1a8/0x3e4
> [  +0.000009]  __platform_driver_register+0x6c/0x94
> [  +0.000008]  meson_drm_platform_driver_init+0x3c/0x1000 [meson_drm]
> [  +0.000027]  do_one_initcall+0xc4/0x2b0
> [  +0.000011]  do_init_module+0x154/0x570
> [  +0.000011]  load_module+0x1a78/0x1ea4
> [  +0.000008]  __do_sys_init_module+0x184/0x1cc
> [  +0.000009]  __arm64_sys_init_module+0x78/0xb0
> [  +0.000009]  invoke_syscall+0x74/0x260
> [  +0.000009]  el0_svc_common.constprop.0+0xcc/0x260
> [  +0.000008]  do_el0_svc+0x50/0x70
> [  +0.000007]  el0_svc+0x68/0x1a0
> [  +0.000012]  el0t_64_sync_handler+0x11c/0x150
> [  +0.000008]  el0t_64_sync+0x18c/0x190
> 
> [  +0.000016] Allocated by task 879:
> [  +0.000008]  kasan_save_stack+0x2c/0x5c
> [  +0.000011]  __kasan_kmalloc+0x90/0xd0
> [  +0.000007]  __kmalloc+0x278/0x4a0
> [  +0.000011]  mpi_resize+0x13c/0x1d0
> [  +0.000011]  mpi_powm+0xd24/0x1570
> [  +0.000009]  rsa_enc+0x1a4/0x30c
> [  +0.000009]  pkcs1pad_verify+0x3f0/0x580
> [  +0.000009]  public_key_verify_signature+0x7a8/0xba4
> [  +0.000010]  public_key_verify_signature_2+0x40/0x60
> [  +0.000008]  verify_signature+0xb4/0x114
> [  +0.000008]  pkcs7_validate_trust_one.constprop.0+0x3b8/0x574
> [  +0.000009]  pkcs7_validate_trust+0xb8/0x15c
> [  +0.000008]  verify_pkcs7_message_sig+0xec/0x1b0
> [  +0.000012]  verify_pkcs7_signature+0x78/0xac
> [  +0.000007]  mod_verify_sig+0x110/0x190
> [  +0.000009]  module_sig_check+0x114/0x1e0
> [  +0.000009]  load_module+0xa0/0x1ea4
> [  +0.000008]  __do_sys_init_module+0x184/0x1cc
> [  +0.000008]  __arm64_sys_init_module+0x78/0xb0
> [  +0.000008]  invoke_syscall+0x74/0x260
> [  +0.000009]  el0_svc_common.constprop.0+0x1a8/0x260
> [  +0.000008]  do_el0_svc+0x50/0x70
> [  +0.000007]  el0_svc+0x68/0x1a0
> [  +0.000009]  el0t_64_sync_handler+0x11c/0x150
> [  +0.000009]  el0t_64_sync+0x18c/0x190
> 
> [  +0.000013] Freed by task 2422:
> [  +0.000008]  kasan_save_stack+0x2c/0x5c
> [  +0.000009]  kasan_set_track+0x2c/0x40
> [  +0.000007]  kasan_set_free_info+0x28/0x50
> [  +0.000009]  ____kasan_slab_free+0x128/0x1d4
> [  +0.000008]  __kasan_slab_free+0x18/0x24
> [  +0.000007]  slab_free_freelist_hook+0x108/0x230
> [  +0.000010]  kfree+0x110/0x35c
> [  +0.000008]  release_nodes+0xf0/0x16c
> [  +0.000009]  devres_release_group+0x180/0x270
> [  +0.000008]  take_down_aggregate_device+0xcc/0x160
> [  +0.000010]  component_del+0x18c/0x360
> [  +0.000009]  meson_dw_hdmi_remove+0x28/0x40 [meson_dw_hdmi]
> [  +0.000013]  platform_remove+0x64/0xb0
> [  +0.000008]  device_remove+0xb8/0x154
> [  +0.000009]  device_release_driver_internal+0x398/0x5b0
> [  +0.000009]  driver_detach+0xac/0x1b0
> [  +0.000009]  bus_remove_driver+0x158/0x29c
> [  +0.000008]  driver_unregister+0x70/0xb0
> [  +0.000009]  platform_driver_unregister+0x20/0x2c
> [  +0.000007]  meson_dw_hdmi_platform_driver_exit+0x1c/0x30 [meson_dw_hdmi]
> [  +0.000012]  __do_sys_delete_module+0x288/0x400
> [  +0.000009]  __arm64_sys_delete_module+0x5c/0x80
> [  +0.000009]  invoke_syscall+0x74/0x260
> [  +0.000008]  el0_svc_common.constprop.0+0xcc/0x260
> [  +0.000008]  do_el0_svc+0x50/0x70
> [  +0.000007]  el0_svc+0x68/0x1a0
> [  +0.000008]  el0t_64_sync_handler+0x11c/0x150
> [  +0.000009]  el0t_64_sync+0x18c/0x190
> 
> [  +0.000013] The buggy address belongs to the object at ffff00003da29000
>                 which belongs to the cache kmalloc-1k of size 1024
> [  +0.000008] The buggy address is located 496 bytes inside of
>                 1024-byte region [ffff00003da29000, ffff00003da29400)
> 
> [  +0.000015] The buggy address belongs to the physical page:
> [  +0.000009] page:fffffc0000f68a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3da28
> [  +0.000012] head:fffffc0000f68a00 order:3 compound_mapcount:0 compound_pincount:0
> [  +0.000009] flags: 0xffff00000010200(slab|head|node=0|zone=0|lastcpupid=0xffff)
> [  +0.000019] raw: 0ffff00000010200 fffffc0000eb5c08 fffffc0000d96608 ffff000000002a80
> [  +0.000008] raw: 0000000000000000 00000000000a000a 00000001ffffffff 0000000000000000
> [  +0.000008] page dumped because: kasan: bad access detected
> 
> [  +0.000011] Memory state around the buggy address:
> [  +0.000009]  ffff00003da29080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [  +0.000007]  ffff00003da29100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [  +0.000007] >ffff00003da29180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [  +0.000007]                                                              ^
> [  +0.000008]  ffff00003da29200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [  +0.000006]  ffff00003da29280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [  +0.000007] ==================================================================
> 
> Fix by keeping track of which encoders were initialised in the meson_drm
> structure and manually removing their bridges at aggregate driver's unbind
> time.
> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
> ---
>   drivers/gpu/drm/meson/meson_drv.c          |  4 ++++
>   drivers/gpu/drm/meson/meson_drv.h          |  7 +++++++
>   drivers/gpu/drm/meson/meson_encoder_cvbs.c | 13 +++++++++++++
>   drivers/gpu/drm/meson/meson_encoder_cvbs.h |  1 +
>   drivers/gpu/drm/meson/meson_encoder_hdmi.c | 13 +++++++++++++
>   drivers/gpu/drm/meson/meson_encoder_hdmi.h |  1 +
>   6 files changed, 39 insertions(+)
> 
> diff --git a/drivers/gpu/drm/meson/meson_drv.c b/drivers/gpu/drm/meson/meson_drv.c
> index 7649df362a85..3b24a924b7b9 100644
> --- a/drivers/gpu/drm/meson/meson_drv.c
> +++ b/drivers/gpu/drm/meson/meson_drv.c
> @@ -390,6 +390,10 @@ static void meson_drv_unbind(struct device *dev)
>   	drm_atomic_helper_shutdown(drm);
>   	free_irq(priv->vsync_irq, drm);
>   	drm_dev_put(drm);
> +
> +	meson_encoder_hdmi_remove(priv);
> +	meson_encoder_cvbs_remove(priv);
> +
>   	component_unbind_all(dev, drm);
>   
>   	if (priv->afbcd.ops)
> diff --git a/drivers/gpu/drm/meson/meson_drv.h b/drivers/gpu/drm/meson/meson_drv.h
> index 177dac3ca3be..c62ee358456f 100644
> --- a/drivers/gpu/drm/meson/meson_drv.h
> +++ b/drivers/gpu/drm/meson/meson_drv.h
> @@ -25,6 +25,12 @@ enum vpu_compatible {
>   	VPU_COMPATIBLE_G12A = 3,
>   };
>   
> +enum {
> +	MESON_ENC_CVBS = 0,
> +	MESON_ENC_HDMI,
> +	MESON_ENC_LAST,
> +};
> +
>   struct meson_drm_match_data {
>   	enum vpu_compatible compat;
>   	struct meson_afbcd_ops *afbcd_ops;
> @@ -51,6 +57,7 @@ struct meson_drm {
>   	struct drm_crtc *crtc;
>   	struct drm_plane *primary_plane;
>   	struct drm_plane *overlay_plane;
> +	void *encoders[MESON_ENC_LAST];
>   
>   	const struct meson_drm_soc_limits *limits;
>   
> diff --git a/drivers/gpu/drm/meson/meson_encoder_cvbs.c b/drivers/gpu/drm/meson/meson_encoder_cvbs.c
> index 8110a6e39320..5675bc2a92cf 100644
> --- a/drivers/gpu/drm/meson/meson_encoder_cvbs.c
> +++ b/drivers/gpu/drm/meson/meson_encoder_cvbs.c
> @@ -281,5 +281,18 @@ int meson_encoder_cvbs_init(struct meson_drm *priv)
>   	}
>   	drm_connector_attach_encoder(connector, &meson_encoder_cvbs->encoder);
>   
> +	priv->encoders[MESON_ENC_CVBS] = meson_encoder_cvbs;
> +
>   	return 0;
>   }
> +
> +void meson_encoder_cvbs_remove(struct meson_drm *priv)
> +{
> +	struct meson_encoder_cvbs *meson_encoder_cvbs;
> +
> +	if (priv->encoders[MESON_ENC_CVBS]) {
> +		meson_encoder_cvbs = priv->encoders[MESON_ENC_CVBS];
> +		drm_bridge_remove(&meson_encoder_cvbs->bridge);
> +		drm_bridge_remove(meson_encoder_cvbs->next_bridge);
> +	}
> +}
> diff --git a/drivers/gpu/drm/meson/meson_encoder_cvbs.h b/drivers/gpu/drm/meson/meson_encoder_cvbs.h
> index 61d9d183ce7f..09710fec3c66 100644
> --- a/drivers/gpu/drm/meson/meson_encoder_cvbs.h
> +++ b/drivers/gpu/drm/meson/meson_encoder_cvbs.h
> @@ -25,5 +25,6 @@ struct meson_cvbs_mode {
>   extern struct meson_cvbs_mode meson_cvbs_modes[MESON_CVBS_MODES_COUNT];
>   
>   int meson_encoder_cvbs_init(struct meson_drm *priv);
> +void meson_encoder_cvbs_remove(struct meson_drm *priv);
>   
>   #endif /* __MESON_VENC_CVBS_H */
> diff --git a/drivers/gpu/drm/meson/meson_encoder_hdmi.c b/drivers/gpu/drm/meson/meson_encoder_hdmi.c
> index 2f616c55c271..53231bfdf7e2 100644
> --- a/drivers/gpu/drm/meson/meson_encoder_hdmi.c
> +++ b/drivers/gpu/drm/meson/meson_encoder_hdmi.c
> @@ -452,6 +452,8 @@ int meson_encoder_hdmi_init(struct meson_drm *priv)
>   		meson_encoder_hdmi->cec_notifier = notifier;
>   	}
>   
> +	priv->encoders[MESON_ENC_HDMI] = meson_encoder_hdmi;
> +
>   	dev_dbg(priv->dev, "HDMI encoder initialized\n");
>   
>   	return 0;
> @@ -460,3 +462,14 @@ int meson_encoder_hdmi_init(struct meson_drm *priv)
>   	of_node_put(remote);
>   	return ret;
>   }
> +
> +void meson_encoder_hdmi_remove(struct meson_drm *priv)
> +{
> +	struct meson_encoder_hdmi *meson_encoder_hdmi;
> +
> +	if (priv->encoders[MESON_ENC_HDMI]) {
> +		meson_encoder_hdmi = priv->encoders[MESON_ENC_HDMI];
> +		drm_bridge_remove(&meson_encoder_hdmi->bridge);
> +		drm_bridge_remove(meson_encoder_hdmi->next_bridge);
> +	}
> +}
> diff --git a/drivers/gpu/drm/meson/meson_encoder_hdmi.h b/drivers/gpu/drm/meson/meson_encoder_hdmi.h
> index ed19494f0956..a6cd38eb5f71 100644
> --- a/drivers/gpu/drm/meson/meson_encoder_hdmi.h
> +++ b/drivers/gpu/drm/meson/meson_encoder_hdmi.h
> @@ -8,5 +8,6 @@
>   #define __MESON_ENCODER_HDMI_H
>   
>   int meson_encoder_hdmi_init(struct meson_drm *priv);
> +void meson_encoder_hdmi_remove(struct meson_drm *priv);
>   
>   #endif /* __MESON_ENCODER_HDMI_H */

Great, thanks !

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>