Messages in this thread Patch in this message | | | From | George Kennedy <> | Subject | [PATCH v2] tun: avoid double free in tun_free_netdev | Date | Mon, 13 Dec 2021 12:04:11 -0500 |
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Avoid double free in tun_free_netdev() by checking if dev->reg_state is NETREG_UNREGISTERING in the tun_set_iff() error paths. If dev->reg_state is NETREG_UNREGISTERING that means the destructor will be called later.
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
Reported-by: syzkaller <syzkaller@googlegroups.com> Signed-off-by: George Kennedy <george.kennedy@oracle.com> --- Jakub, decided to go the less code churn route and just check for dev->reg_state is NETREG_UNREGISTERING.
drivers/net/tun.c | 21 +++++++-------------- 1 file changed, 7 insertions(+), 14 deletions(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 1572878..9ab530a 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -2206,10 +2206,6 @@ static void tun_free_netdev(struct net_device *dev) BUG_ON(!(list_empty(&tun->disabled))); free_percpu(dev->tstats); - /* We clear tstats so that tun_set_iff() can tell if - * tun_free_netdev() has been called from register_netdevice(). - */ - dev->tstats = NULL; tun_flow_uninit(tun); security_tun_dev_free_security(tun->security); @@ -2770,18 +2766,15 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) err_detach: tun_detach_all(dev); - /* We are here because register_netdevice() has failed. - * If register_netdevice() already called tun_free_netdev() - * while dealing with the error, dev->stats has been cleared. - */ - if (!dev->tstats) - goto err_free_dev; - err_free_flow: - tun_flow_uninit(tun); - security_tun_dev_free_security(tun->security); + /* if NETREG_UNREGISTERING, destructor will be called later */ + if (dev->reg_state != NETREG_UNREGISTERING) { + tun_flow_uninit(tun); + security_tun_dev_free_security(tun->security); + } err_free_stat: - free_percpu(dev->tstats); + if (dev->reg_state != NETREG_UNREGISTERING) + free_percpu(dev->tstats); err_free_dev: free_netdev(dev); return err; -- 1.8.3.1
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