virtiofs: fix memory leak in virtio_fs_probe()

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

virtiofs: fix memory leak in virtio_fs_probe()

When accidentally passing twice the same tag to qemu, kmemleak ended up

reporting a memory leak in virtiofs. Also, looking at the log I saw the

following error (that's when I realised the duplicated tag):

virtiofs: probe of virtio5 failed with error -17

Here's the kmemleak log for reference:

unreferenced object 0xffff888103d47800 (size 1024):

comm "systemd-udevd", pid 118, jiffies 4294893780 (age 18.340s)

hex dump (first 32 bytes):

00 00 00 00 ad 4e ad de ff ff ff ff 00 00 00 00 .....N..........

ff ff ff ff ff ff ff ff 80 90 02 a0 ff ff ff ff ................

backtrace:

[<000000000ebb87c1>] virtio_fs_probe+0x171/0x7ae [virtiofs]

[<00000000f8aca419>] virtio_dev_probe+0x15f/0x210

[<000000004d6baf3c>] really_probe+0xea/0x430

[<00000000a6ceeac8>] device_driver_attach+0xa8/0xb0

[<00000000196f47a7>] __driver_attach+0x98/0x140

[<000000000b20601d>] bus_for_each_dev+0x7b/0xc0

[<00000000399c7b7f>] bus_add_driver+0x11b/0x1f0

[<0000000032b09ba7>] driver_register+0x8f/0xe0

[<00000000cdd55998>] 0xffffffffa002c013

[<000000000ea196a2>] do_one_initcall+0x64/0x2e0

[<0000000008f727ce>] do_init_module+0x5c/0x260

[<000000003cdedab6>] __do_sys_finit_module+0xb5/0x120

[<00000000ad2f48c6>] do_syscall_64+0x33/0x40

[<00000000809526b5>] entry_SYSCALL_64_after_hwframe+0x44/0xae