CVE-2021-47237: In the Linux kernel, the following vulnerability has been resolved:  net: hamradio: fix memory leak in mkiss_close  My local syzbot instance hit memory leak in mkiss_open()[1]. The problem was in missing free_netdev() in mkiss_close().  In mkiss_open() netdevice is allocated and then registered, but in mkiss_close() netdevice was only unregistered, but not freed.  Fail log:  BUG: memory leak unreferenced object 0xffff8880281ba000 (size 4096):   comm "syz-executor.1", pid 11443, jiffies 4295046091 (age 17.660s)   hex dump (first 32 bytes):     61 78 30 00 00 00 00 00 00 00 00 00 00 00 00 00  ax0.............     00 27 fa 2a 80 88 ff ff 00 00 00 00 00 00 00 00  .'.*............   backtrace:     [<ffffffff81a27201>] kvmalloc_node+0x61/0xf0     [<ffffffff8706e7e8>] alloc_netdev_mqs+0x98/0xe80     [<ffffffff84e64192>] mkiss_open+0xb2/0x6f0 [1]     [<ffffffff842355db>] tty_ldisc_open+0x9b/0x110     [<ffffffff84236488>] tty_set_ldisc+0x2e8/0x670     [<ffffffff8421f7f3>] tty_ioctl+0xda3/0x1440     [<ffffffff81c9f273>] __x64_sys_ioctl+0x193/0x200     [<ffffffff8911263a>] do_syscall_64+0x3a/0xb0     [<ffffffff89200068>] entry_SYSCALL_64_after_hwframe+0x44/0xae  BUG: memory leak unreferenced object 0xffff8880141a9a00 (size 96):   comm "syz-executor.1", pid 11443, jiffies 4295046091 (age 17.660s)   hex dump (first 32 bytes):     e8 a2 1b 28 80 88 ff ff e8 a2 1b 28 80 88 ff ff  ...(.......(....     98 92 9c aa b0 40 02 00 00 00 00 00 00 00 00 00  .....@..........   backtrace:     [<ffffffff8709f68b>] __hw_addr_create_ex+0x5b/0x310     [<ffffffff8709fb38>] __hw_addr_add_ex+0x1f8/0x2b0     [<ffffffff870a0c7b>] dev_addr_init+0x10b/0x1f0     [<ffffffff8706e88b>] alloc_netdev_mqs+0x13b/0xe80     [<ffffffff84e64192>] mkiss_open+0xb2/0x6f0 [1]     [<ffffffff842355db>] tty_ldisc_open+0x9b/0x110     [<ffffffff84236488>] tty_set_ldisc+0x2e8/0x670     [<ffffffff8421f7f3>] tty_ioctl+0xda3/0x1440     [<ffffffff81c9f273>] __x64_sys_ioctl+0x193/0x200     [<ffffffff8911263a>] do_syscall_64+0x3a/0xb0     [<ffffffff89200068>] entry_SYSCALL_64_after_hwframe+0x44/0xae  BUG: memory leak unreferenced object 0xffff8880219bfc00 (size 512):   comm "syz-executor.1", pid 11443, jiffies 4295046091 (age 17.660s)   hex dump (first 32 bytes):     00 a0 1b 28 80 88 ff ff 80 8f b1 8d ff ff ff ff  ...(............     80 8f b1 8d ff ff ff ff 00 00 00 00 00 00 00 00  ................   backtrace:     [<ffffffff81a27201>] kvmalloc_node+0x61/0xf0     [<ffffffff8706eec7>] alloc_netdev_mqs+0x777/0xe80     [<ffffffff84e64192>] mkiss_open+0xb2/0x6f0 [1]     [<ffffffff842355db>] tty_ldisc_open+0x9b/0x110     [<ffffffff84236488>] tty_set_ldisc+0x2e8/0x670     [<ffffffff8421f7f3>] tty_ioctl+0xda3/0x1440     [<ffffffff81c9f273>] __x64_sys_ioctl+0x193/0x200     [<ffffffff8911263a>] do_syscall_64+0x3a/0xb0     [<ffffffff89200068>] entry_SYSCALL_64_after_hwframe+0x44/0xae  BUG: memory leak unreferenced object 0xffff888029b2b200 (size 256):   comm "syz-executor.1", pid 11443, jiffies 4295046091 (age 17.660s)   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:     [<ffffffff81a27201>] kvmalloc_node+0x61/0xf0     [<ffffffff8706f062>] alloc_netdev_mqs+0x912/0xe80     [<ffffffff84e64192>] mkiss_open+0xb2/0x6f0 [1]     [<ffffffff842355db>] tty_ldisc_open+0x9b/0x110     [<ffffffff84236488>] tty_set_ldisc+0x2e8/0x670     [<ffffffff8421f7f3>] tty_ioctl+0xda3/0x1440     [<ffffffff81c9f273>] __x64_sys_ioctl+0x193/0x200     [<ffffffff8911263a>] do_syscall_64+0x3a/0xb0     [<ffffffff89200068>] entry_SYSCALL_64_after_hwframe+0x44/0xae