[PATCH v2 0/1] Fix use-after-free on framebuffers and property blobs when calling drm_dev_unplug

[PATCH v2 0/1] Fix use-after-free on framebuffers and property blobs when calling drm_dev_unplug

[Maarten Lankhorst]

I tried to see what happened with xe_module_unload --r reload on a fully
running system, and came across these bugs in the kernel. Even after
these fixes I still see a hang when reloading, related to cgroups, so
likely some more fixes are needed to address those.

Should this patch have a fixes tag or cc stable patch?

Test-with: https://patchwork.freedesktop.org/series/162133/

Maarten Lankhorst (1):
  drm: Fix use-after-free on framebuffers and property blobs when
    calling drm_dev_unplug

 drivers/gpu/drm/drm_file.c        | 5 ++++-
 drivers/gpu/drm/drm_mode_config.c | 9 ++++++---
 2 files changed, 10 insertions(+), 4 deletions(-)

-- 
2.51.0

[PATCH v2 1/1] drm: Fix use-after-free on framebuffers and property blobs when calling drm_dev_unplug

[Maarten Lankhorst]

When trying to do a rather aggressive test of igt's "xe_module_load
--r reload" with a full desktop environment and game running I noticed
a few OOPSes when dereferencing freed pointers, related to
framebuffers and property blobs after the compositor exits.

Solve this by guarding the freeing in drm_file with drm_dev_enter/exit,
and immediately put the references from struct drm_file objects during
drm_dev_unplug().

Related warnings for framebuffers on the subtest:
[  739.713076] ------------[ cut here ]------------
               WARN_ON(!list_empty(&dev->mode_config.fb_list))
[  739.713079] WARNING: drivers/gpu/drm/drm_mode_config.c:584 at drm_mode_config_cleanup+0x30b/0x320 [drm], CPU#12: xe_module_load/13145
....
[  739.713328] Call Trace:
[  739.713330]  <TASK>
[  739.713335]  ? intel_pmdemand_destroy_state+0x11/0x20 [xe]
[  739.713574]  ? intel_atomic_global_obj_cleanup+0xe4/0x1a0 [xe]
[  739.713794]  intel_display_driver_remove_noirq+0x51/0xb0 [xe]
[  739.714041]  xe_display_fini_early+0x33/0x50 [xe]
[  739.714284]  devm_action_release+0xf/0x20
[  739.714294]  devres_release_all+0xad/0xf0
[  739.714301]  device_unbind_cleanup+0x12/0xa0
[  739.714305]  device_release_driver_internal+0x1b7/0x210
[  739.714311]  device_driver_detach+0x14/0x20
[  739.714315]  unbind_store+0xa6/0xb0
[  739.714319]  drv_attr_store+0x21/0x30
[  739.714322]  sysfs_kf_write+0x48/0x60
[  739.714328]  kernfs_fop_write_iter+0x16b/0x240
[  739.714333]  vfs_write+0x266/0x520
[  739.714341]  ksys_write+0x72/0xe0
[  739.714345]  __x64_sys_write+0x19/0x20
[  739.714347]  x64_sys_call+0xa15/0xa30
[  739.714355]  do_syscall_64+0xd8/0xab0
[  739.714361]  entry_SYSCALL_64_after_hwframe+0x4b/0x53

and

[  739.714459] ------------[ cut here ]------------
[  739.714461] xe 0000:67:00.0: [drm] drm_WARN_ON(!list_empty(&fb->filp_head))
[  739.714464] WARNING: drivers/gpu/drm/drm_framebuffer.c:833 at drm_framebuffer_free+0x6c/0x90 [drm], CPU#12: xe_module_load/13145
[  739.714715] RIP: 0010:drm_framebuffer_free+0x7a/0x90 [drm]
...
[  739.714869] Call Trace:
[  739.714871]  <TASK>
[  739.714876]  drm_mode_config_cleanup+0x26a/0x320 [drm]
[  739.714998]  ? __drm_printfn_seq_file+0x20/0x20 [drm]
[  739.715115]  ? drm_mode_config_cleanup+0x207/0x320 [drm]
[  739.715235]  intel_display_driver_remove_noirq+0x51/0xb0 [xe]
[  739.715576]  xe_display_fini_early+0x33/0x50 [xe]
[  739.715821]  devm_action_release+0xf/0x20
[  739.715828]  devres_release_all+0xad/0xf0
[  739.715843]  device_unbind_cleanup+0x12/0xa0
[  739.715850]  device_release_driver_internal+0x1b7/0x210
[  739.715856]  device_driver_detach+0x14/0x20
[  739.715860]  unbind_store+0xa6/0xb0
[  739.715865]  drv_attr_store+0x21/0x30
[  739.715868]  sysfs_kf_write+0x48/0x60
[  739.715873]  kernfs_fop_write_iter+0x16b/0x240
[  739.715878]  vfs_write+0x266/0x520
[  739.715886]  ksys_write+0x72/0xe0
[  739.715890]  __x64_sys_write+0x19/0x20
[  739.715893]  x64_sys_call+0xa15/0xa30
[  739.715900]  do_syscall_64+0xd8/0xab0
[  739.715905]  entry_SYSCALL_64_after_hwframe+0x4b/0x53

and then finally file close blows up:

[  743.186530] Oops: general protection fault, probably for non-canonical address 0xdead000000000122: 0000 [#1] SMP
[  743.186535] CPU: 3 UID: 1000 PID: 3453 Comm: kwin_wayland Tainted: G        W           7.0.0-rc1-valkyria+ #110 PREEMPT_{RT,(lazy)}
[  743.186537] Tainted: [W]=WARN
[  743.186538] Hardware name: Gigabyte Technology Co., Ltd. X299 AORUS Gaming 3/X299 AORUS Gaming 3-CF, BIOS F8n 12/06/2021
[  743.186539] RIP: 0010:drm_framebuffer_cleanup+0x55/0xc0 [drm]
[  743.186588] Code: d8 72 73 0f b6 42 05 ff c3 39 c3 72 e8 49 8d bd 50 07 00 00 31 f6 e8 3a 80 d3 e1 49 8b 44 24 10 49 8d 7c 24 08 49 8b 54 24 08 <48> 3b 38 0f 85 95 7f 02 00 48 3b 7a 08 0f 85 8b 7f 02 00 48 89 42
[  743.186589] RSP: 0018:ffffc900085e3cf8 EFLAGS: 00010202
[  743.186591] RAX: dead000000000122 RBX: 0000000000000001 RCX: ffffffff8217ed03
[  743.186592] RDX: dead000000000100 RSI: 0000000000000000 RDI: ffff88814675ba08
[  743.186593] RBP: ffffc900085e3d10 R08: 0000000000000000 R09: 0000000000000000
[  743.186593] R10: 0000000000000000 R11: 0000000000000000 R12: ffff88814675ba00
[  743.186594] R13: ffff88810d778000 R14: ffff888119f6dca0 R15: ffff88810c660bb0
[  743.186595] FS:  00007ff377d21280(0000) GS:ffff888cec3f8000(0000) knlGS:0000000000000000
[  743.186596] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  743.186596] CR2: 000055690b55e000 CR3: 0000000113586003 CR4: 00000000003706f0
[  743.186597] Call Trace:
[  743.186598]  <TASK>
[  743.186603]  intel_user_framebuffer_destroy+0x12/0x90 [xe]
[  743.186722]  drm_framebuffer_free+0x3a/0x90 [drm]
[  743.186750]  ? trace_hardirqs_on+0x5f/0x120
[  743.186754]  drm_mode_object_put+0x51/0x70 [drm]
[  743.186786]  drm_fb_release+0x105/0x190 [drm]
[  743.186812]  ? rt_mutex_slowunlock+0x3aa/0x410
[  743.186817]  ? rt_spin_lock+0xea/0x1b0
[  743.186819]  drm_file_free+0x1e0/0x2c0 [drm]
[  743.186843]  drm_release_noglobal+0x91/0xf0 [drm]
[  743.186865]  __fput+0x100/0x2e0
[  743.186869]  fput_close_sync+0x40/0xa0
[  743.186870]  __x64_sys_close+0x3e/0x80
[  743.186873]  x64_sys_call+0xa07/0xa30
[  743.186879]  do_syscall_64+0xd8/0xab0
[  743.186881]  entry_SYSCALL_64_after_hwframe+0x4b/0x53
[  743.186882] RIP: 0033:0x7ff37e567732
[  743.186884] Code: 08 0f 85 a1 38 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 55 bf 01 00
[  743.186885] RSP: 002b:00007ffc818169a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
[  743.186886] RAX: ffffffffffffffda RBX: 00007ffc81816a30 RCX: 00007ff37e567732
[  743.186887] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000012
[  743.186888] RBP: 00007ffc818169d0 R08: 0000000000000000 R09: 0000000000000000
[  743.186889] R10: 0000000000000000 R11: 0000000000000246 R12: 000055d60a7996e0
[  743.186889] R13: 00007ffc81816a90 R14: 00007ffc81816a90 R15: 000055d60a782a30
[  743.186892]  </TASK>
[  743.186893] Modules linked in: rfcomm snd_hrtimer xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp xt_addrtype nft_compat x_tables nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables overlay cfg80211 bnep mtd_intel_dg snd_hda_codec_intelhdmi mtd snd_hda_codec_hdmi nls_utf8 mxm_wmi intel_wmi_thunderbolt gigabyte_wmi wmi_bmof xe drm_gpuvm drm_gpusvm_helper i2c_algo_bit drm_buddy drm_ttm_helper ttm video drm_suballoc_helper gpu_sched drm_client_lib drm_exec drm_display_helper cec drm_kunit_helpers drm_kms_helper kunit x86_pkg_temp_thermal intel_powerclamp coretemp snd_hda_codec_alc882 snd_hda_codec_realtek_lib snd_hda_codec_generic snd_hda_intel snd_soc_avs snd_soc_hda_codec snd_hda_ext_core snd_hda_codec snd_hwdep snd_hda_core snd_intel_dspcfg snd_soc_core snd_compress ac97_bus snd_pcm snd_seq snd_seq_device snd_timer i2c_i801 i2c_mux snd i2c_smbus btusb btrtl btbcm btmtk btintel bluetooth ecdh_generic rfkill ecc mei_me mei ioatdma dca wmi nfsd drm i2c_dev fuse nfnetlink
[  743.186938] ---[ end trace 0000000000000000 ]---

And for property blobs:

void drm_mode_config_cleanup(struct drm_device *dev)
{
...
	list_for_each_entry_safe(blob, bt, &dev->mode_config.property_blob_list,
				 head_global) {
		drm_property_blob_put(blob);
	}

Resulting in:

[  371.072940] BUG: unable to handle page fault for address: 000001ffffffffff
[  371.072944] #PF: supervisor read access in kernel mode
[  371.072945] #PF: error_code(0x0000) - not-present page
[  371.072947] PGD 0 P4D 0
[  371.072950] Oops: Oops: 0000 [#1] SMP
[  371.072953] CPU: 0 UID: 1000 PID: 3693 Comm: kwin_wayland Not tainted 7.0.0-rc1-valkyria+ #111 PREEMPT_{RT,(lazy)}
[  371.072956] Hardware name: Gigabyte Technology Co., Ltd. X299 AORUS Gaming 3/X299 AORUS Gaming 3-CF, BIOS F8n 12/06/2021
[  371.072957] RIP: 0010:drm_property_destroy_user_blobs+0x3b/0x90 [drm]
[  371.073019] Code: 00 00 48 83 ec 10 48 8b 86 30 01 00 00 48 39 c3 74 59 48 89 c2 48 8d 48 c8 48 8b 00 4c 8d 60 c8 eb 04 4c 8d 60 c8 48 8b 71 40 <48> 39 16 0f 85 39 32 01 00 48 3b 50 08 0f 85 2f 32 01 00 48 89 70
[  371.073021] RSP: 0018:ffffc90006a73de8 EFLAGS: 00010293
[  371.073022] RAX: 000001ffffffffff RBX: ffff888118a1a930 RCX: ffff8881b92355c0
[  371.073024] RDX: ffff8881b92355f8 RSI: 000001ffffffffff RDI: ffff888118be4000
[  371.073025] RBP: ffffc90006a73e08 R08: ffff8881009b7300 R09: ffff888cecc5b000
[  371.073026] R10: ffffc90006a73e90 R11: 0000000000000002 R12: 000001ffffffffc7
[  371.073027] R13: ffff888118a1a980 R14: ffff88810b366d20 R15: ffff888118a1a970
[  371.073028] FS:  00007f1faccbb280(0000) GS:ffff888cec2db000(0000) knlGS:0000000000000000
[  371.073029] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  371.073030] CR2: 000001ffffffffff CR3: 000000010655c001 CR4: 00000000003706f0
[  371.073031] Call Trace:
[  371.073033]  <TASK>
[  371.073036]  drm_file_free+0x1df/0x2a0 [drm]
[  371.073077]  drm_release_noglobal+0x7a/0xe0 [drm]
[  371.073113]  __fput+0xe2/0x2b0
[  371.073118]  fput_close_sync+0x40/0xa0
[  371.073119]  __x64_sys_close+0x3e/0x80
[  371.073122]  x64_sys_call+0xa07/0xa30
[  371.073126]  do_syscall_64+0xc0/0x840
[  371.073130]  entry_SYSCALL_64_after_hwframe+0x4b/0x53
[  371.073132] RIP: 0033:0x7f1fb3501732
[  371.073133] Code: 08 0f 85 a1 38 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 55 bf 01 00
[  371.073135] RSP: 002b:00007ffe8e6f0278 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
[  371.073136] RAX: ffffffffffffffda RBX: 00007ffe8e6f0300 RCX: 00007f1fb3501732
[  371.073137] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000012
[  371.073138] RBP: 00007ffe8e6f02a0 R08: 0000000000000000 R09: 0000000000000000
[  371.073139] R10: 0000000000000000 R11: 0000000000000246 R12: 00005585ba46eea0
[  371.073140] R13: 00007ffe8e6f0360 R14: 00007ffe8e6f0360 R15: 00005585ba458a30
[  371.073143]  </TASK>
[  371.073144] Modules linked in: rfcomm snd_hrtimer xt_addrtype xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp nft_compat x_tables nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables overlay cfg80211 bnep snd_hda_codec_intelhdmi snd_hda_codec_hdmi mtd_intel_dg mtd nls_utf8 wmi_bmof mxm_wmi gigabyte_wmi intel_wmi_thunderbolt xe drm_gpuvm drm_gpusvm_helper i2c_algo_bit drm_buddy drm_ttm_helper ttm video drm_suballoc_helper gpu_sched drm_client_lib drm_exec drm_display_helper cec drm_kunit_helpers drm_kms_helper kunit x86_pkg_temp_thermal intel_powerclamp coretemp snd_hda_codec_alc882 snd_hda_codec_realtek_lib snd_hda_codec_generic snd_hda_intel snd_soc_avs snd_soc_hda_codec snd_hda_ext_core snd_hda_codec snd_hwdep snd_hda_core snd_intel_dspcfg snd_soc_core snd_compress ac97_bus snd_pcm snd_seq snd_seq_device snd_timer i2c_i801 btusb i2c_mux i2c_smbus btrtl snd btbcm btmtk btintel bluetooth ecdh_generic rfkill ecc mei_me mei ioatdma dca wmi nfsd drm i2c_dev fuse nfnetlink
[  371.073198] CR2: 000001ffffffffff
[  371.073199] ---[ end trace 0000000000000000 ]---

Add a guard around file close, and ensure the warnings from drm_mode_config
do not trigger. Fix those by allowing an open reference to the file descriptor
and cleaning up the file linked list entry in drm_mode_config_cleanup().

Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
---
 drivers/gpu/drm/drm_file.c        | 5 ++++-
 drivers/gpu/drm/drm_mode_config.c | 9 ++++++---
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index ec820686b3021..f52141f842a1f 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -233,6 +233,7 @@ static void drm_events_release(struct drm_file *file_priv)
 void drm_file_free(struct drm_file *file)
 {
 	struct drm_device *dev;
+	int idx;
 
 	if (!file)
 		return;
@@ -249,9 +250,11 @@ void drm_file_free(struct drm_file *file)
 
 	drm_events_release(file);
 
-	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
+	if (drm_core_check_feature(dev, DRIVER_MODESET) &&
+	    drm_dev_enter(dev, &idx)) {
 		drm_fb_release(file);
 		drm_property_destroy_user_blobs(dev, file);
+		drm_dev_exit(idx);
 	}
 
 	if (drm_core_check_feature(dev, DRIVER_SYNCOBJ))
diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
index 84ae8a23a3678..e349418978f79 100644
--- a/drivers/gpu/drm/drm_mode_config.c
+++ b/drivers/gpu/drm/drm_mode_config.c
@@ -583,10 +583,13 @@ void drm_mode_config_cleanup(struct drm_device *dev)
 	 */
 	WARN_ON(!list_empty(&dev->mode_config.fb_list));
 	list_for_each_entry_safe(fb, fbt, &dev->mode_config.fb_list, head) {
-		struct drm_printer p = drm_dbg_printer(dev, DRM_UT_KMS, "[leaked fb]");
+		if (list_empty(&fb->filp_head) || drm_framebuffer_read_refcount(fb) > 1) {
+			struct drm_printer p = drm_dbg_printer(dev, DRM_UT_KMS, "[leaked fb]");
 
-		drm_printf(&p, "framebuffer[%u]:\n", fb->base.id);
-		drm_framebuffer_print_info(&p, 1, fb);
+			drm_printf(&p, "framebuffer[%u]:\n", fb->base.id);
+			drm_framebuffer_print_info(&p, 1, fb);
+		}
+		list_del_init(&fb->filp_head);
 		drm_framebuffer_free(&fb->base.refcount);
 	}
 
-- 
2.51.0

Claude review: drm: Fix use-after-free on framebuffers and property blobs when calling drm_dev_unplug

[Claude Code Review Bot]

Patch Review

**The `drm_file_free` change (drm_file.c):**

The `drm_dev_enter`/`drm_dev_exit` guard is a reasonable approach to skip `drm_fb_release()` and `drm_property_destroy_user_blobs()` when the device has been unplugged:

```c
if (drm_core_check_feature(dev, DRIVER_MODESET) &&
    drm_dev_enter(dev, &idx)) {
	drm_fb_release(file);
	drm_property_destroy_user_blobs(dev, file);
	drm_dev_exit(idx);
}
```

However, this raises a **resource leak concern**: if `drm_dev_enter` fails (device unplugged), we skip both `drm_fb_release` and `drm_property_destroy_user_blobs` entirely. This means the refcounts held by the file's `fbs` list and `blobs` list are never dropped. The patch relies on `drm_mode_config_cleanup()` to handle cleanup instead, but:

1. For framebuffers: `drm_mode_config_cleanup` calls `drm_framebuffer_free` which bypasses `kref_put` and directly invokes the free path. This works to destroy the objects but is unusual — it forcibly frees regardless of refcount.

2. For property blobs: the `property_blob_list` iteration in `drm_mode_config_cleanup` drops the global list reference, but the per-file `head_file` list reference from `file_priv->blobs` is never cleaned up. If a blob has both a global reference and a per-file reference, the per-file `drm_property_blob_put` is skipped, potentially leaking the blob entirely since `drm_mode_config_cleanup` only drops the `head_global` reference.

**The `drm_mode_config_cleanup` change (drm_mode_config.c):**

```c
if (list_empty(&fb->filp_head) || drm_framebuffer_read_refcount(fb) > 1) {
	struct drm_printer p = drm_dbg_printer(dev, DRM_UT_KMS, "[leaked fb]");

	drm_printf(&p, "framebuffer[%u]:\n", fb->base.id);
	drm_framebuffer_print_info(&p, 1, fb);
}
list_del_init(&fb->filp_head);
drm_framebuffer_free(&fb->base.refcount);
```

Several issues here:

1. **The `list_del_init(&fb->filp_head)` is done to satisfy the `drm_WARN_ON(!list_empty(&fb->filp_head))` in `drm_framebuffer_free`** (drm_framebuffer.c:833). This is correct in intent — these fbs still have a `filp_head` because `drm_fb_release` was skipped — but it papers over the problem by just detaching the node right before the check.

2. **The diagnostic condition is inverted in meaning**: the original code unconditionally printed leaked fb info. The new condition `list_empty(&fb->filp_head) || refcount > 1` prints the warning only for fbs that either have no file association (truly leaked) or have extra references. But fbs that are on the `filp_head` list with refcount == 1 (the normal unplug case) are silently freed. This seems intentional but the logic is a bit subtle and deserves a comment.

3. **Calling `drm_framebuffer_free(&fb->base.refcount)` directly** bypasses `kref_put`, so it doesn't check whether the refcount is actually zero. If any other code path still holds a reference (e.g. an in-flight atomic commit), this will cause a double-free. The original code had the same pattern, so this isn't a regression, but it's worth noting.

4. **No corresponding fix for property blobs**: The cover letter and commit message mention property blob crashes, and the `drm_file_free` change skips `drm_property_destroy_user_blobs`, but there's no change to the blob cleanup path in `drm_mode_config_cleanup`. The blobs on `file_priv->blobs` are never cleaned up — their `head_file` links still point into the (about-to-be-freed) file structure. This seems like an incomplete fix. The blob list iteration at `drm_mode_config.c:571` walks `head_global`, so it won't encounter the per-file references, meaning blobs created by the user could leak.

**Missing `Fixes:` tag**: The cover letter asks whether this should have a fixes tag. Yes — this is clearly a bug fix for a crash/oops, so a `Fixes:` tag pointing to the commit that introduced `drm_dev_unplug` (or the relevant mode_config cleanup) and `Cc: stable@vger.kernel.org` would be appropriate.

**Summary of concerns:**
- The property blob cleanup appears incomplete — skipping `drm_property_destroy_user_blobs` in `drm_file_free` without compensating in `drm_mode_config_cleanup` may leak blobs
- The approach of directly calling `drm_framebuffer_free` (bypassing kref) is fragile if any other references exist
- A `Fixes:` tag and `Cc: stable` should be added
- The conditional leak-warning logic in `drm_mode_config_cleanup` could use a brief comment explaining the reasoning

---
Generated by Claude Code Patch Reviewer

Claude review: Fix use-after-free on framebuffers and property blobs when calling drm_dev_unplug

[Claude Code Review Bot]

Overall Series Review

Subject: Fix use-after-free on framebuffers and property blobs when calling drm_dev_unplug
Author: Maarten Lankhorst <dev@lankhorst.se>
Patches: 2
Reviewed: 2026-03-14T06:45:34.233027

---

This single-patch series addresses a real use-after-free bug that occurs during `drm_dev_unplug` (hot-unplug / module reload) when userspace clients still have open file descriptors. The race is: the device gets torn down via `drm_mode_config_cleanup()` which frees framebuffers and blobs, but then userspace closes its fd and `drm_file_free()` tries to walk the now-freed `filp_head`/`head_file` lists — resulting in the oopses shown in the commit message.

The approach has the right idea — skip the fb/blob cleanup in `drm_file_free` when the device is already unplugged — but there are several concerns with the implementation.

---
Generated by Claude Code Patch Reviewer