iommu: Fix crash during syfs iommu_groups/N/type

The err_restore_domain flow was accidently inserted into the success path
in commit 1000dcc ("iommu: Allow IOMMU_RESV_DIRECT to work on
ARM"). It should only happen if iommu_create_device_direct_mappings()
fails. This caused the domains the be wrongly changed and freed whenever
the sysfs is used, resulting in an oops:

  BUG: kernel NULL pointer dereference, address: 0000000000000000
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 0 P4D 0
  Oops: 0000 [#1] PREEMPT SMP NOPTI
  CPU: 1 PID: 3417 Comm: avocado Not tainted 6.4.0-rc4-next-20230602 #3
  Hardware name: Dell Inc. PowerEdge R6515/07PXPY, BIOS 2.3.6 07/06/2021
  RIP: 0010:__iommu_attach_device+0xc/0xa0
  Code: c0 c3 cc cc cc cc 48 89 f0 c3 cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1f 44 00 00 41 54 55 48 8b 47 08 <48> 8b 00 48 85 c0 74 74 48 89 f5 e8 64 12 49 00 41 89 c4 85 c0 74
  RSP: 0018:ffffabae0220bd48 EFLAGS: 00010246
  RAX: 0000000000000000 RBX: ffff9ac04f70e410 RCX: 0000000000000001
  RDX: ffff9ac044db20c0 RSI: ffff9ac044fa50d0 RDI: ffff9ac04f70e410
  RBP: ffff9ac044fa50d0 R08: 1000000100209001 R09: 00000000000002dc
  R10: 0000000000000000 R11: 0000000000000000 R12: ffff9ac043d54700
  R13: ffff9ac043d54700 R14: 0000000000000001 R15: 0000000000000001
  FS:  00007f02e30ae000(0000) GS:ffff9afeb2440000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000000000 CR3: 000000012afca006 CR4: 0000000000770ee0
  PKRU: 55555554
  Call Trace:
   <TASK>
   ? __die+0x24/0x70
   ? page_fault_oops+0x82/0x150
   ? __iommu_queue_command_sync+0x80/0xc0
   ? exc_page_fault+0x69/0x150
   ? asm_exc_page_fault+0x26/0x30
   ? __iommu_attach_device+0xc/0xa0
   ? __iommu_attach_device+0x1c/0xa0
   __iommu_device_set_domain+0x42/0x80
   __iommu_group_set_domain_internal+0x5d/0x160
   iommu_setup_default_domain+0x318/0x400
   iommu_group_store_type+0xb1/0x200
   kernfs_fop_write_iter+0x12f/0x1c0
   vfs_write+0x2a2/0x3b0
   ksys_write+0x63/0xe0
   do_syscall_64+0x3f/0x90
   entry_SYSCALL_64_after_hwframe+0x6e/0xd8
  RIP: 0033:0x7f02e2f14a6f

Reorganize the error flow so that the success branch and error branches
are clearer.

Fixes: 1000dcc ("iommu: Allow IOMMU_RESV_DIRECT to work on ARM")
Reported-by: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
Tested-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/0-v1-5bd8cc969d9e+1f1-iommu_set_def_fix_jgg@nvidia.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: jgunthorpe

drivers/iommu/iommu.c

@@ -2891,14 +2891,11 @@ static int iommu_setup_default_domain(struct iommu_group *group,
 		ret = __iommu_group_set_domain_internal(
 			group, dom, IOMMU_SET_DOMAIN_MUST_SUCCEED);
 		if (WARN_ON(ret))
-			goto out_free;
+			goto out_free_old;
 	} else {
 		ret = __iommu_group_set_domain(group, dom);
-		if (ret) {
-			iommu_domain_free(dom);
-			group->default_domain = old_dom;
-			return ret;
-		}
+		if (ret)
+			goto err_restore_def_domain;
 	}
 
 	/*
@@ -2911,20 +2908,24 @@ static int iommu_setup_default_domain(struct iommu_group *group,
 		for_each_group_device(group, gdev) {
 			ret = iommu_create_device_direct_mappings(dom, gdev->dev);
 			if (ret)
-				goto err_restore;
+				goto err_restore_domain;
 		}
 	}
 
-err_restore:
-	if (old_dom) {
+out_free_old:
+	if (old_dom)
+		iommu_domain_free(old_dom);
+	return ret;
+
+err_restore_domain:
+	if (old_dom)
 		__iommu_group_set_domain_internal(
 			group, old_dom, IOMMU_SET_DOMAIN_MUST_SUCCEED);
+err_restore_def_domain:
+	if (old_dom) {
 		iommu_domain_free(dom);
-		old_dom = NULL;
+		group->default_domain = old_dom;
 	}
-out_free:
-	if (old_dom)
-		iommu_domain_free(old_dom);
 	return ret;
 }