floppy: Fix memory leak in do_floppy_init()

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

floppy: Fix memory leak in do_floppy_init()

A memory leak was reported when floppy_alloc_disk() failed in
do_floppy_init().

unreferenced object 0xffff888115ed25a0 (size 8):
comm "modprobe", pid 727, jiffies 4295051278 (age 25.529s)
hex dump (first 8 bytes):
00 ac 67 5b 81 88 ff ff ..g[....
backtrace:
[<000000007f457abb>] __kmalloc_node+0x4c/0xc0
[<00000000a87bfa9e>] blk_mq_realloc_tag_set_tags.part.0+0x6f/0x180
[<000000006f02e8b1>] blk_mq_alloc_tag_set+0x573/0x1130
[<0000000066007fd7>] 0xffffffffc06b8b08
[<0000000081f5ac40>] do_one_initcall+0xd0/0x4f0
[<00000000e26d04ee>] do_init_module+0x1a4/0x680
[<000000001bb22407>] load_module+0x6249/0x7110
[<00000000ad31ac4d>] __do_sys_finit_module+0x140/0x200
[<000000007bddca46>] do_syscall_64+0x35/0x80
[<00000000b5afec39>] entry_SYSCALL_64_after_hwframe+0x46/0xb0
unreferenced object 0xffff88810fc30540 (size 32):
comm "modprobe", pid 727, jiffies 4295051278 (age 25.529s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<000000007f457abb>] __kmalloc_node+0x4c/0xc0
[<000000006b91eab4>] blk_mq_alloc_tag_set+0x393/0x1130
[<0000000066007fd7>] 0xffffffffc06b8b08
[<0000000081f5ac40>] do_one_initcall+0xd0/0x4f0
[<00000000e26d04ee>] do_init_module+0x1a4/0x680
[<000000001bb22407>] load_module+0x6249/0x7110
[<00000000ad31ac4d>] __do_sys_finit_module+0x140/0x200
[<000000007bddca46>] do_syscall_64+0x35/0x80
[<00000000b5afec39>] entry_SYSCALL_64_after_hwframe+0x46/0xb0

If the floppy_alloc_disk() failed, disks of current drive will not be set,
thus the lastest allocated set->tag cannot be freed in the error handling
path. A simple call graph shown as below:

floppy_module_init()
floppy_init()
do_floppy_init()
for (drive = 0; drive < N_DRIVE; drive++)
blk_mq_alloc_tag_set()
blk_mq_alloc_tag_set_tags()
blk_mq_realloc_tag_set_tags() # set->tag allocated
floppy_alloc_disk()
blk_mq_alloc_disk() # error occurred, disks failed to allocated

->out_put_disk:
for (drive = 0; drive < N_DRIVE; drive++)
if (!disks[drive][0]) # the last disks is not set and loop break
break;
blk_mq_free_tag_set() # the latest allocated set->tag leaked

Fix this problem by free the set->tag of current drive before jump to
error handling path.

[efremov: added stable list, changed title]