NFS4: Fix oops when copy_file_range is attempted with NFS4.0 source

[ Upstream commit d8a6ad9 ]

The following oops is seen during xfstest/565 when the 'test'
(source of the copy) is NFS4.0 and 'scratch' (destination) is NFS4.2
[   59.692458] run fstests generic/565 at 2020-08-01 05:50:35
[   60.613588] BUG: kernel NULL pointer dereference, address: 0000000000000008
[   60.624970] #PF: supervisor read access in kernel mode
[   60.627671] #PF: error_code(0x0000) - not-present page
[   60.630347] PGD 0 P4D 0
[   60.631853] Oops: 0000 [#1] SMP PTI
[   60.634086] CPU: 6 PID: 2828 Comm: xfs_io Kdump: loaded Not tainted 5.8.0-rc3 #1
[   60.637676] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
[   60.639901] RIP: 0010:nfs4_check_serverowner_major_id+0x5/0x30 [nfsv4]
[   60.642719] Code: 89 ff e8 3e b3 b8 e1 e9 71 fe ff ff 41 bc da d8 ff ff e9 c3 fe ff ff e8 e9 9d 08 e2 66 0f 1f 84 00 00 00 00 00 66 66 66 66 90 <8b> 57 08 31 c0 3b 56 08 75 12 48 83 c6 0c 48 83 c7 0c e8 c4 97 bb
[   60.652629] RSP: 0018:ffffc265417f7e10 EFLAGS: 00010287
[   60.655379] RAX: ffffa0664b066400 RBX: 0000000000000000 RCX: 0000000000000001
[   60.658754] RDX: ffffa066725fb000 RSI: ffffa066725fd000 RDI: 0000000000000000
[   60.662292] RBP: 0000000000020000 R08: 0000000000020000 R09: 0000000000000000
[   60.666189] R10: 0000000000000003 R11: 0000000000000000 R12: ffffa06648258d00
[   60.669914] R13: 0000000000000000 R14: 0000000000000000 R15: ffffa06648258100
[   60.673645] FS:  00007faa9fb35800(0000) GS:ffffa06677d80000(0000) knlGS:0000000000000000
[   60.677698] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   60.680773] CR2: 0000000000000008 CR3: 0000000203f14000 CR4: 00000000000406e0
[   60.684476] Call Trace:
[   60.685809]  nfs4_copy_file_range+0xfc/0x230 [nfsv4]
[   60.688704]  vfs_copy_file_range+0x2ee/0x310
[   60.691104]  __x64_sys_copy_file_range+0xd6/0x210
[   60.693527]  do_syscall_64+0x4d/0x90
[   60.695512]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[   60.698006] RIP: 0033:0x7faa9febc1bd

Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

fs/nfs/nfs4file.c

@@ -138,7 +138,8 @@ static ssize_t __nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
 	/* Only offload copy if superblock is the same */
 	if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
 		return -EXDEV;
-	if (!nfs_server_capable(file_inode(file_out), NFS_CAP_COPY))
+	if (!nfs_server_capable(file_inode(file_out), NFS_CAP_COPY) ||
+	    !nfs_server_capable(file_inode(file_in), NFS_CAP_COPY))
 		return -EOPNOTSUPP;
 	if (file_inode(file_in) == file_inode(file_out))
 		return -EOPNOTSUPP;