CVE-2021-47082

In the Linux kernel, the following vulnerability has been resolved: tun:
avoid double free in tun_free_netdev Avoid double free in tun_free_netdev()
by moving the dev->tstats and tun->security allocs to a new ndo_init
routine (tun_net_init()) that will be called by register_netdevice().
ndo_init is paired with the desctructor (tun_free_netdev()), so if there’s
an error in register_netdevice() the destructor will handle the frees. BUG:
KASAN: double-free or invalid-free in
selinux_tun_dev_free_security+0x1a/0x20 security/selinux/hooks.c:5605 CPU:
0 PID: 25750 Comm: syz-executor416 Not tainted 5.16.0-rc2-syzk #1 Hardware
name: Red Hat KVM, BIOS Call Trace: <TASK> __dump_stack lib/dump_stack.c:88
[inline] dump_stack_lvl+0x89/0xb5 lib/dump_stack.c:106
print_address_description.constprop.9+0x28/0x160 mm/kasan/report.c:247
kasan_report_invalid_free+0x55/0x80 mm/kasan/report.c:372
____kasan_slab_free mm/kasan/common.c:346 [inline]
__kasan_slab_free+0x107/0x120 mm/kasan/common.c:374 kasan_slab_free
include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:1723 [inline]
slab_free_freelist_hook mm/slub.c:1749 [inline] slab_free mm/slub.c:3513
[inline] kfree+0xac/0x2d0 mm/slub.c:4561
selinux_tun_dev_free_security+0x1a/0x20 security/selinux/hooks.c:5605
security_tun_dev_free_security+0x4f/0x90 security/security.c:2342
tun_free_netdev+0xe6/0x150 drivers/net/tun.c:2215
netdev_run_todo+0x4df/0x840 net/core/dev.c:10627 rtnl_unlock+0x13/0x20
net/core/rtnetlink.c:112 __tun_chr_ioctl+0x80c/0x2870
drivers/net/tun.c:3302 tun_chr_ioctl+0x2f/0x40 drivers/net/tun.c:3311
vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline] __x64_sys_ioctl+0x19d/0x220
fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae