From f75a2804da391571563c4b6b29e7797787332673 Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Thu, 31 Jan 2019 13:05:49 -0800 Subject: xfrm: destroy xfrm_state synchronously on net exit path xfrm_state_put() moves struct xfrm_state to the GC list and schedules the GC work to clean it up. On net exit call path, xfrm_state_flush() is called to clean up and xfrm_flush_gc() is called to wait for the GC work to complete before exit. However, this doesn't work because one of the ->destructor(), ipcomp_destroy(), schedules the same GC work again inside the GC work. It is hard to wait for such a nested async callback. This is also why syzbot still reports the following warning: WARNING: CPU: 1 PID: 33 at net/ipv6/xfrm6_tunnel.c:351 xfrm6_tunnel_net_exit+0x2cb/0x500 net/ipv6/xfrm6_tunnel.c:351 ... ops_exit_list.isra.0+0xb0/0x160 net/core/net_namespace.c:153 cleanup_net+0x51d/0xb10 net/core/net_namespace.c:551 process_one_work+0xd0c/0x1ce0 kernel/workqueue.c:2153 worker_thread+0x143/0x14a0 kernel/workqueue.c:2296 kthread+0x357/0x430 kernel/kthread.c:246 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352 In fact, it is perfectly fine to bypass GC and destroy xfrm_state synchronously on net exit call path, because it is in process context and doesn't need a work struct to do any blocking work. This patch introduces xfrm_state_put_sync() which simply bypasses GC, and lets its callers to decide whether to use this synchronous version. On net exit path, xfrm_state_fini() and xfrm6_tunnel_net_exit() use it. And, as ipcomp_destroy() itself is blocking, it can use xfrm_state_put_sync() directly too. Also rename xfrm_state_gc_destroy() to ___xfrm_state_destroy() to reflect this change. Fixes: b48c05ab5d32 ("xfrm: Fix warning in xfrm6_tunnel_net_exit.") Reported-and-tested-by: syzbot+e9aebef558e3ed673934@syzkaller.appspotmail.com Cc: Steffen Klassert Signed-off-by: Cong Wang Signed-off-by: Steffen Klassert --- include/net/xfrm.h | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) (limited to 'include/net/xfrm.h') diff --git a/include/net/xfrm.h b/include/net/xfrm.h index 7298a53b9702..85386becbaea 100644 --- a/include/net/xfrm.h +++ b/include/net/xfrm.h @@ -853,7 +853,7 @@ static inline void xfrm_pols_put(struct xfrm_policy **pols, int npols) xfrm_pol_put(pols[i]); } -void __xfrm_state_destroy(struct xfrm_state *); +void __xfrm_state_destroy(struct xfrm_state *, bool); static inline void __xfrm_state_put(struct xfrm_state *x) { @@ -863,7 +863,13 @@ static inline void __xfrm_state_put(struct xfrm_state *x) static inline void xfrm_state_put(struct xfrm_state *x) { if (refcount_dec_and_test(&x->refcnt)) - __xfrm_state_destroy(x); + __xfrm_state_destroy(x, false); +} + +static inline void xfrm_state_put_sync(struct xfrm_state *x) +{ + if (refcount_dec_and_test(&x->refcnt)) + __xfrm_state_destroy(x, true); } static inline void xfrm_state_hold(struct xfrm_state *x) @@ -1590,7 +1596,7 @@ struct xfrmk_spdinfo { struct xfrm_state *xfrm_find_acq_byseq(struct net *net, u32 mark, u32 seq); int xfrm_state_delete(struct xfrm_state *x); -int xfrm_state_flush(struct net *net, u8 proto, bool task_valid); +int xfrm_state_flush(struct net *net, u8 proto, bool task_valid, bool sync); int xfrm_dev_state_flush(struct net *net, struct net_device *dev, bool task_valid); void xfrm_sad_getinfo(struct net *net, struct xfrmk_sadinfo *si); void xfrm_spd_getinfo(struct net *net, struct xfrmk_spdinfo *si); -- cgit v1.2.3