From 91341fa0003befd097e190ec2a4bf63ad957c49a Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 13 Jan 2022 01:22:29 -0800 Subject: inet: frags: annotate races around fqdir->dead and fqdir->high_thresh Both fields can be read/written without synchronization, add proper accessors and documentation. Fixes: d5dd88794a13 ("inet: fix various use-after-free in defrags units") Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/inet_frag.h | 11 +++++++++-- include/net/ipv6_frag.h | 3 ++- 2 files changed, 11 insertions(+), 3 deletions(-) (limited to 'include/net') diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h index 48cc5795ceda..63540be0fc34 100644 --- a/include/net/inet_frag.h +++ b/include/net/inet_frag.h @@ -117,8 +117,15 @@ int fqdir_init(struct fqdir **fqdirp, struct inet_frags *f, struct net *net); static inline void fqdir_pre_exit(struct fqdir *fqdir) { - fqdir->high_thresh = 0; /* prevent creation of new frags */ - fqdir->dead = true; + /* Prevent creation of new frags. + * Pairs with READ_ONCE() in inet_frag_find(). + */ + WRITE_ONCE(fqdir->high_thresh, 0); + + /* Pairs with READ_ONCE() in inet_frag_kill(), ip_expire() + * and ip6frag_expire_frag_queue(). + */ + WRITE_ONCE(fqdir->dead, true); } void fqdir_exit(struct fqdir *fqdir); diff --git a/include/net/ipv6_frag.h b/include/net/ipv6_frag.h index 851029ecff13..0a4779175a52 100644 --- a/include/net/ipv6_frag.h +++ b/include/net/ipv6_frag.h @@ -67,7 +67,8 @@ ip6frag_expire_frag_queue(struct net *net, struct frag_queue *fq) struct sk_buff *head; rcu_read_lock(); - if (fq->q.fqdir->dead) + /* Paired with the WRITE_ONCE() in fqdir_pre_exit(). */ + if (READ_ONCE(fq->q.fqdir->dead)) goto out_rcu_unlock; spin_lock(&fq->q.lock); -- cgit v1.2.3