smb: client: fix NULL ptr deref in cifs_mark_open_handles_for_deleted_file()

cifs_get_fattr() may be called with a NULL inode, so check for a
non-NULL inode before calling
cifs_mark_open_handles_for_deleted_file().

This fixes the following oops:

  mount.cifs //srv/share /mnt -o ...,vers=3.1.1
  cd /mnt
  touch foo; tail -f foo &
  rm foo
  cat foo

  BUG: kernel NULL pointer dereference, address: 00000000000005c0
  #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: 2 PID: 696 Comm: cat Not tainted 6.9.0-rc2 #1
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
  1.16.3-1.fc39 04/01/2014
  RIP: 0010:__lock_acquire+0x5d/0x1c70
  Code: 00 00 44 8b a4 24 a0 00 00 00 45 85 f6 0f 84 bb 06 00 00 8b 2d
  48 e2 95 01 45 89 c3 41 89 d2 45 89 c8 85 ed 0 0 <48> 81 3f 40 7a 76
  83 44 0f 44 d8 83 fe 01 0f 86 1b 03 00 00 31 d2
  RSP: 0018:ffffc90000b37490 EFLAGS: 00010002
  RAX: 0000000000000000 RBX: ffff888110021ec0 RCX: 0000000000000000
  RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000000005c0
  RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
  R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000200
  FS: 00007f2a1fa08740(0000) GS:ffff888157a00000(0000)
  knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0:
  0000000080050033
  CR2: 00000000000005c0 CR3: 000000011ac7c000 CR4: 0000000000750ef0
  PKRU: 55555554
  Call Trace:
   <TASK>
   ? __die+0x23/0x70
   ? page_fault_oops+0x180/0x490
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? exc_page_fault+0x70/0x230
   ? asm_exc_page_fault+0x26/0x30
   ? __lock_acquire+0x5d/0x1c70
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? srso_alias_return_thunk+0x5/0xfbef5
   lock_acquire+0xc0/0x2d0
   ? cifs_mark_open_handles_for_deleted_file+0x3a/0x100 [cifs]
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? kmem_cache_alloc+0x2d9/0x370
   _raw_spin_lock+0x34/0x80
   ? cifs_mark_open_handles_for_deleted_file+0x3a/0x100 [cifs]
   cifs_mark_open_handles_for_deleted_file+0x3a/0x100 [cifs]
   cifs_get_fattr+0x24c/0x940 [cifs]
   ? srso_alias_return_thunk+0x5/0xfbef5
   cifs_get_inode_info+0x96/0x120 [cifs]
   cifs_lookup+0x16e/0x800 [cifs]
   cifs_atomic_open+0xc7/0x5d0 [cifs]
   ? lookup_open.isra.0+0x3ce/0x5f0
   ? __pfx_cifs_atomic_open+0x10/0x10 [cifs]
   lookup_open.isra.0+0x3ce/0x5f0
   path_openat+0x42b/0xc30
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? srso_alias_return_thunk+0x5/0xfbef5
   ? srso_alias_return_thunk+0x5/0xfbef5
   do_filp_open+0xc4/0x170
   do_sys_openat2+0xab/0xe0
   __x64_sys_openat+0x57/0xa0
   do_syscall_64+0xc1/0x1e0
   entry_SYSCALL_64_after_hwframe+0x72/0x7a

Fixes: ffceb764 ("smb: client: do not defer close open handles to deleted files")
Reviewed-by: Meetakshi Setiya <msetiya@microsoft.com>
Reviewed-by: Bharath SM <bharathsm@microsoft.com>
Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/client/inode.c

@@ -1105,7 +1105,8 @@ static int cifs_get_fattr(struct cifs_open_info_data *data,
 		} else {
 			cifs_open_info_to_fattr(fattr, data, sb);
 		}
-		if (!rc && fattr->cf_flags & CIFS_FATTR_DELETE_PENDING)
+		if (!rc && *inode &&
+		    (fattr->cf_flags & CIFS_FATTR_DELETE_PENDING))
 			cifs_mark_open_handles_for_deleted_file(*inode, full_path);
 		break;
 	case -EREMOTE: