| Message ID | 20221124175134.1589053-1-syoshida@redhat.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 5daadc86f27ea4d691e2131c04310d0418c6cd12 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v3] net: tun: Fix use-after-free in tun_detach() | expand |
Hello: This patch was applied to netdev/net.git (master) by Paolo Abeni <pabeni@redhat.com>: On Fri, 25 Nov 2022 02:51:34 +0900 you wrote: > syzbot reported use-after-free in tun_detach() [1]. This causes call > trace like below: > > ================================================================== > BUG: KASAN: use-after-free in notifier_call_chain+0x1ee/0x200 kernel/notifier.c:75 > Read of size 8 at addr ffff88807324e2a8 by task syz-executor.0/3673 > > [...] Here is the summary with links: - [v3] net: tun: Fix use-after-free in tun_detach() https://git.kernel.org/netdev/net/c/5daadc86f27e You are awesome, thank you!
diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 7a3ab3427369..24001112c323 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -686,7 +686,6 @@ static void __tun_detach(struct tun_file *tfile, bool clean) if (tun) xdp_rxq_info_unreg(&tfile->xdp_rxq); ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free); - sock_put(&tfile->sk); } } @@ -702,6 +701,9 @@ static void tun_detach(struct tun_file *tfile, bool clean) if (dev) netdev_state_change(dev); rtnl_unlock(); + + if (clean) + sock_put(&tfile->sk); } static void tun_detach_all(struct net_device *dev)
syzbot reported use-after-free in tun_detach() [1]. This causes call trace like below: ================================================================== BUG: KASAN: use-after-free in notifier_call_chain+0x1ee/0x200 kernel/notifier.c:75 Read of size 8 at addr ffff88807324e2a8 by task syz-executor.0/3673 CPU: 0 PID: 3673 Comm: syz-executor.0 Not tainted 6.1.0-rc5-syzkaller-00044-gcc675d22e422 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:284 [inline] print_report+0x15e/0x461 mm/kasan/report.c:395 kasan_report+0xbf/0x1f0 mm/kasan/report.c:495 notifier_call_chain+0x1ee/0x200 kernel/notifier.c:75 call_netdevice_notifiers_info+0x86/0x130 net/core/dev.c:1942 call_netdevice_notifiers_extack net/core/dev.c:1983 [inline] call_netdevice_notifiers net/core/dev.c:1997 [inline] netdev_wait_allrefs_any net/core/dev.c:10237 [inline] netdev_run_todo+0xbc6/0x1100 net/core/dev.c:10351 tun_detach drivers/net/tun.c:704 [inline] tun_chr_close+0xe4/0x190 drivers/net/tun.c:3467 __fput+0x27c/0xa90 fs/file_table.c:320 task_work_run+0x16f/0x270 kernel/task_work.c:179 exit_task_work include/linux/task_work.h:38 [inline] do_exit+0xb3d/0x2a30 kernel/exit.c:820 do_group_exit+0xd4/0x2a0 kernel/exit.c:950 get_signal+0x21b1/0x2440 kernel/signal.c:2858 arch_do_signal_or_restart+0x86/0x2300 arch/x86/kernel/signal.c:869 exit_to_user_mode_loop kernel/entry/common.c:168 [inline] exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:203 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296 do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x63/0xcd The cause of the issue is that sock_put() from __tun_detach() drops last reference count for struct net, and then notifier_call_chain() from netdev_state_change() accesses that struct net. This patch fixes the issue by calling sock_put() from tun_detach() after all necessary accesses for the struct net has done. Fixes: 83c1f36f9880 ("tun: send netlink notification when the device is modified") Reported-by: syzbot+106f9b687cd64ee70cd1@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=96eb7f1ce75ef933697f24eeab928c4a716edefe [1] Signed-off-by: Shigeru Yoshida <syoshida@redhat.com> --- v3: - Remove redundant synchronize_rcu() v2: - Include symbolic stack trace - Add Fixes and Reported-by tags v1: https://lore.kernel.org/all/20221119075615.723290-1-syoshida@redhat.com/ --- drivers/net/tun.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)