| Message ID | 20240802080730.3206303-1-razor@blackwall.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 92c4ee25208d0f35dafc3213cdf355fbe449e078 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] net: bridge: mcast: wait for previous gc cycles when removing port | expand |
Hello: This patch was applied to netdev/net.git (main) by Jakub Kicinski <kuba@kernel.org>: On Fri, 2 Aug 2024 11:07:30 +0300 you wrote: > syzbot hit a use-after-free[1] which is caused because the bridge doesn't > make sure that all previous garbage has been collected when removing a > port. What happens is: > CPU 1 CPU 2 > start gc cycle remove port > acquire gc lock first > wait for lock > call br_multicasg_gc() directly > acquire lock now but free port > the port can be freed > while grp timers still > running > > [...] Here is the summary with links: - [net] net: bridge: mcast: wait for previous gc cycles when removing port https://git.kernel.org/netdev/net/c/92c4ee25208d You are awesome, thank you!
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c index 9a1cb5079a7a..b2ae0d2434d2 100644 --- a/net/bridge/br_multicast.c +++ b/net/bridge/br_multicast.c @@ -2045,16 +2045,14 @@ void br_multicast_del_port(struct net_bridge_port *port) { struct net_bridge *br = port->br; struct net_bridge_port_group *pg; - HLIST_HEAD(deleted_head); struct hlist_node *n; /* Take care of the remaining groups, only perm ones should be left */ spin_lock_bh(&br->multicast_lock); hlist_for_each_entry_safe(pg, n, &port->mglist, mglist) br_multicast_find_del_pg(br, pg); - hlist_move_list(&br->mcast_gc_list, &deleted_head); spin_unlock_bh(&br->multicast_lock); - br_multicast_gc(&deleted_head); + flush_work(&br->mcast_gc_work); br_multicast_port_ctx_deinit(&port->multicast_ctx); free_percpu(port->mcast_stats); }
syzbot hit a use-after-free[1] which is caused because the bridge doesn't make sure that all previous garbage has been collected when removing a port. What happens is: CPU 1 CPU 2 start gc cycle remove port acquire gc lock first wait for lock call br_multicasg_gc() directly acquire lock now but free port the port can be freed while grp timers still running Make sure all previous gc cycles have finished by using flush_work before freeing the port. [1] BUG: KASAN: slab-use-after-free in br_multicast_port_group_expired+0x4c0/0x550 net/bridge/br_multicast.c:861 Read of size 8 at addr ffff888071d6d000 by task syz.5.1232/9699 CPU: 1 PID: 9699 Comm: syz.5.1232 Not tainted 6.10.0-rc5-syzkaller-00021-g24ca36a562d6 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024 Call Trace: <IRQ> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114 print_address_description mm/kasan/report.c:377 [inline] print_report+0xc3/0x620 mm/kasan/report.c:488 kasan_report+0xd9/0x110 mm/kasan/report.c:601 br_multicast_port_group_expired+0x4c0/0x550 net/bridge/br_multicast.c:861 call_timer_fn+0x1a3/0x610 kernel/time/timer.c:1792 expire_timers kernel/time/timer.c:1843 [inline] __run_timers+0x74b/0xaf0 kernel/time/timer.c:2417 __run_timer_base kernel/time/timer.c:2428 [inline] __run_timer_base kernel/time/timer.c:2421 [inline] run_timer_base+0x111/0x190 kernel/time/timer.c:2437 Reported-by: syzbot+263426984509be19c9a0@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=263426984509be19c9a0 Fixes: e12cec65b554 ("net: bridge: mcast: destroy all entries via gc") Signed-off-by: Nikolay Aleksandrov <razor@blackwall.org> --- note: tested with KASAN and kmemleak on. net/bridge/br_multicast.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)