net: mana: cleanup mana struct after debugfs_remove()

When on a MANA VM hibernation is triggered, as part of hibernate_snapshot(),
mana_gd_suspend() and mana_gd_resume() are called. If during this
mana_gd_resume(), a failure occurs with HWC creation, mana_port_debugfs
pointer does not get reinitialized and ends up pointing to older,
cleaned-up dentry.
Further in the hibernation path, as part of power_down(), mana_gd_shutdown()
is triggered. This call, unaware of the failures in resume, tries to cleanup
the already cleaned up  mana_port_debugfs value and hits the following bug:

[  191.359296] mana 7870:00:00.0: Shutdown was called
[  191.359918] BUG: kernel NULL pointer dereference, address: 0000000000000098
[  191.360584] #PF: supervisor write access in kernel mode
[  191.361125] #PF: error_code(0x0002) - not-present page
[  191.361727] PGD 1080ea067 P4D 0
[  191.362172] Oops: Oops: 0002 [#1] SMP NOPTI
[  191.362606] CPU: 11 UID: 0 PID: 1674 Comm: bash Not tainted 6.14.0-rc5+ #2
[  191.363292] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 11/21/2024
[  191.364124] RIP: 0010:down_write+0x19/0x50
[  191.364537] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1f 44 00 00 55 48 89 e5 53 48 89 fb e8 de cd ff ff 31 c0 ba 01 00 00 00 <f0> 48 0f b1 13 75 16 65 48 8b 05 88 24 4c 6a 48 89 43 08 48 8b 5d
[  191.365867] RSP: 0000:ff45fbe0c1c037b8 EFLAGS: 00010246
[  191.366350] RAX: 0000000000000000 RBX: 0000000000000098 RCX: ffffff8100000000
[  191.366951] RDX: 0000000000000001 RSI: 0000000000000064 RDI: 0000000000000098
[  191.367600] RBP: ff45fbe0c1c037c0 R08: 0000000000000000 R09: 0000000000000001
[  191.368225] R10: ff45fbe0d2b01000 R11: 0000000000000008 R12: 0000000000000000
[  191.368874] R13: 000000000000000b R14: ff43dc27509d67c0 R15: 0000000000000020
[  191.369549] FS:  00007dbc5001e740(0000) GS:ff43dc663f380000(0000) knlGS:0000000000000000
[  191.370213] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  191.370830] CR2: 0000000000000098 CR3: 0000000168e8e002 CR4: 0000000000b73ef0
[  191.371557] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  191.372192] DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
[  191.372906] Call Trace:
[  191.373262]  <TASK>
[  191.373621]  ? show_regs+0x64/0x70
[  191.374040]  ? __die+0x24/0x70
[  191.374468]  ? page_fault_oops+0x290/0x5b0
[  191.374875]  ? do_user_addr_fault+0x448/0x800
[  191.375357]  ? exc_page_fault+0x7a/0x160
[  191.375971]  ? asm_exc_page_fault+0x27/0x30
[  191.376416]  ? down_write+0x19/0x50
[  191.376832]  ? down_write+0x12/0x50
[  191.377232]  simple_recursive_removal+0x4a/0x2a0
[  191.377679]  ? __pfx_remove_one+0x10/0x10
[  191.378088]  debugfs_remove+0x44/0x70
[  191.378530]  mana_detach+0x17c/0x4f0
[  191.378950]  ? __flush_work+0x1e2/0x3b0
[  191.379362]  ? __cond_resched+0x1a/0x50
[  191.379787]  mana_remove+0xf2/0x1a0
[  191.380193]  mana_gd_shutdown+0x3b/0x70
[  191.380642]  pci_device_shutdown+0x3a/0x80
[  191.381063]  device_shutdown+0x13e/0x230
[  191.381480]  kernel_power_off+0x35/0x80
[  191.381890]  hibernate+0x3c6/0x470
[  191.382312]  state_store+0xcb/0xd0
[  191.382734]  kobj_attr_store+0x12/0x30
[  191.383211]  sysfs_kf_write+0x3e/0x50
[  191.383640]  kernfs_fop_write_iter+0x140/0x1d0
[  191.384106]  vfs_write+0x271/0x440
[  191.384521]  ksys_write+0x72/0xf0
[  191.384924]  __x64_sys_write+0x19/0x20
[  191.385313]  x64_sys_call+0x2b0/0x20b0
[  191.385736]  do_syscall_64+0x79/0x150
[  191.386146]  ? __mod_memcg_lruvec_state+0xe7/0x240
[  191.386676]  ? __lruvec_stat_mod_folio+0x79/0xb0
[  191.387124]  ? __pfx_lru_add+0x10/0x10
[  191.387515]  ? queued_spin_unlock+0x9/0x10
[  191.387937]  ? do_anonymous_page+0x33c/0xa00
[  191.388374]  ? __handle_mm_fault+0xcf3/0x1210
[  191.388805]  ? __count_memcg_events+0xbe/0x180
[  191.389235]  ? handle_mm_fault+0xae/0x300
[  191.389588]  ? do_user_addr_fault+0x559/0x800
[  191.390027]  ? irqentry_exit_to_user_mode+0x43/0x230
[  191.390525]  ? irqentry_exit+0x1d/0x30
[  191.390879]  ? exc_page_fault+0x86/0x160
[  191.391235]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[  191.391745] RIP: 0033:0x7dbc4ff1c574
[  191.392111] Code: c7 00 16 00 00 00 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 80 3d d5 ea 0e 00 00 74 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 55 48 89 e5 48 83 ec 20 48 89
[  191.393412] RSP: 002b:00007ffd95a23ab8 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
[  191.393990] RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00007dbc4ff1c574
[  191.394594] RDX: 0000000000000005 RSI: 00005a6eeadb0ce0 RDI: 0000000000000001
[  191.395215] RBP: 00007ffd95a23ae0 R08: 00007dbc50003b20 R09: 0000000000000000
[  191.395805] R10: 0000000000000001 R11: 0000000000000202 R12: 0000000000000005
[  191.396404] R13: 00005a6eeadb0ce0 R14: 00007dbc500045c0 R15: 00007dbc50001ee0
[  191.396987]  </TASK>

To fix this, we explicitly set such mana debugfs variables to NULL after
debugfs_remove() is called.

Fixes: 6607c17 ("net: mana: Enable debugfs files for MANA device")
Cc: [email protected]
Signed-off-by: Shradha Gupta <[email protected]>
Reviewed-by: Haiyang Zhang <[email protected]>
Reviewed-by: Michal Kubiak <[email protected]>
Link: https://patch.msgid.link/1741688260-28922-1-git-send-email-shradhagupta@linux.microsoft.com
Signed-off-by: Paolo Abeni <[email protected]>

Author: Shradha Gupta

drivers/net/ethernet/microsoft/mana/gdma_main.c

@@ -1547,6 +1547,7 @@ static int mana_gd_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	 * adapter-MTU file and apc->mana_pci_debugfs folder.
 	 */
 	debugfs_remove_recursive(gc->mana_pci_debugfs);
+	gc->mana_pci_debugfs = NULL;
 	pci_iounmap(pdev, bar0_va);
 free_gc:
 	pci_set_drvdata(pdev, NULL);
@@ -1569,6 +1570,8 @@ static void mana_gd_remove(struct pci_dev *pdev)
 
 	debugfs_remove_recursive(gc->mana_pci_debugfs);
 
+	gc->mana_pci_debugfs = NULL;
+
 	pci_iounmap(pdev, gc->bar0_va);
 
 	vfree(gc);
@@ -1622,6 +1625,8 @@ static void mana_gd_shutdown(struct pci_dev *pdev)
 
 	debugfs_remove_recursive(gc->mana_pci_debugfs);
 
+	gc->mana_pci_debugfs = NULL;
+
 	pci_disable_device(pdev);
 }
 
@@ -1648,8 +1653,10 @@ static int __init mana_driver_init(void)
 	mana_debugfs_root = debugfs_create_dir("mana", NULL);
 
 	err = pci_register_driver(&mana_driver);
-	if (err)
+	if (err) {
 		debugfs_remove(mana_debugfs_root);
+		mana_debugfs_root = NULL;
+	}
 
 	return err;
 }
@@ -1659,6 +1666,8 @@ static void __exit mana_driver_exit(void)
 	pci_unregister_driver(&mana_driver);
 
 	debugfs_remove(mana_debugfs_root);
+
+	mana_debugfs_root = NULL;
 }
 
 module_init(mana_driver_init);

drivers/net/ethernet/microsoft/mana/mana_en.c

@@ -738,12 +738,11 @@ static const struct net_device_ops mana_devops = {
 static void mana_cleanup_port_context(struct mana_port_context *apc)
 {
 	/*
-	 * at this point all dir/files under the vport directory
-	 * are already cleaned up.
-	 * We are sure the apc->mana_port_debugfs remove will not
-	 * cause any freed memory access issues
+	 * make sure subsequent cleanup attempts don't end up removing already
+	 * cleaned dentry pointer
 	 */
 	debugfs_remove(apc->mana_port_debugfs);
+	apc->mana_port_debugfs = NULL;
 	kfree(apc->rxqs);
 	apc->rxqs = NULL;
 }
@@ -1254,6 +1253,7 @@ static void mana_destroy_eq(struct mana_context *ac)
 		return;
 
 	debugfs_remove_recursive(ac->mana_eqs_debugfs);
+	ac->mana_eqs_debugfs = NULL;
 
 	for (i = 0; i < gc->max_num_queues; i++) {
 		eq = ac->eqs[i].eq;
@@ -1914,6 +1914,7 @@ static void mana_destroy_txq(struct mana_port_context *apc)
 
 	for (i = 0; i < apc->num_queues; i++) {
 		debugfs_remove_recursive(apc->tx_qp[i].mana_tx_debugfs);
+		apc->tx_qp[i].mana_tx_debugfs = NULL;
 
 		napi = &apc->tx_qp[i].tx_cq.napi;
 		if (apc->tx_qp[i].txq.napi_initialized) {
@@ -2099,6 +2100,7 @@ static void mana_destroy_rxq(struct mana_port_context *apc,
 		return;
 
 	debugfs_remove_recursive(rxq->mana_rx_debugfs);
+	rxq->mana_rx_debugfs = NULL;
 
 	napi = &rxq->rx_cq.napi;