cifs: Fix use-after-free in rdata->read_into_pages()

In the Linux kernel, the following vulnerability has been resolved:

cifs: Fix use-after-free in rdata->read_into_pages()

When the network status is unstable, use-after-free may occur when
read data from the server.

BUG: KASAN: use-after-free in readpages_fill_pages+0x14c/0x7e0

Call Trace:
<TASK>
dump_stack_lvl+0x38/0x4c
print_report+0x16f/0x4a6
kasan_report+0xb7/0x130
readpages_fill_pages+0x14c/0x7e0
cifs_readv_receive+0x46d/0xa40
cifs_demultiplex_thread+0x121c/0x1490
kthread+0x16b/0x1a0
ret_from_fork+0x2c/0x50
</TASK>

Allocated by task 2535:
kasan_save_stack+0x22/0x50
kasan_set_track+0x25/0x30
__kasan_kmalloc+0x82/0x90
cifs_readdata_direct_alloc+0x2c/0x110
cifs_readdata_alloc+0x2d/0x60
cifs_readahead+0x393/0xfe0
read_pages+0x12f/0x470
page_cache_ra_unbounded+0x1b1/0x240
filemap_get_pages+0x1c8/0x9a0
filemap_read+0x1c0/0x540
cifs_strict_readv+0x21b/0x240
vfs_read+0x395/0x4b0
ksys_read+0xb8/0x150
do_syscall_64+0x3f/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc

Freed by task 79:
kasan_save_stack+0x22/0x50
kasan_set_track+0x25/0x30
kasan_save_free_info+0x2e/0x50
__kasan_slab_free+0x10e/0x1a0
__kmem_cache_free+0x7a/0x1a0
cifs_readdata_release+0x49/0x60
process_one_work+0x46c/0x760
worker_thread+0x2a4/0x6f0
kthread+0x16b/0x1a0
ret_from_fork+0x2c/0x50

Last potentially related work creation:
kasan_save_stack+0x22/0x50
__kasan_record_aux_stack+0x95/0xb0
insert_work+0x2b/0x130
__queue_work+0x1fe/0x660
queue_work_on+0x4b/0x60
smb2_readv_callback+0x396/0x800
cifs_abort_connection+0x474/0x6a0
cifs_reconnect+0x5cb/0xa50
cifs_readv_from_socket.cold+0x22/0x6c
cifs_read_page_from_socket+0xc1/0x100
readpages_fill_pages.cold+0x2f/0x46
cifs_readv_receive+0x46d/0xa40
cifs_demultiplex_thread+0x121c/0x1490
kthread+0x16b/0x1a0
ret_from_fork+0x2c/0x50

The following function calls will cause UAF of the rdata pointer.

readpages_fill_pages
cifs_read_page_from_socket
cifs_readv_from_socket
cifs_reconnect
__cifs_reconnect
cifs_abort_connection
mid->callback() --> smb2_readv_callback
queue_work(&rdata->work) # if the worker completes first,
# the rdata is freed
cifs_readv_complete
kref_put
cifs_readdata_release
kfree(rdata)
return rdata->... # UAF in readpages_fill_pages()

Similarly, this problem also occurs in the uncache_fill_pages().

Fix this by adjusts the order of condition judgment in the return
statement.