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Date: Thu, 13 Jan 2022 01:22:29 -0800 From: Eric Dumazet <eric.dumazet@...il.com> To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org> Cc: netdev <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>, Eric Dumazet <eric.dumazet@...il.com> Subject: [PATCH net] inet: frags: annotate races around fqdir->dead and fqdir->high_thresh From: Eric Dumazet <edumazet@...gle.com> 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 <edumazet@...gle.com> --- include/net/inet_frag.h | 11 +++++++++-- include/net/ipv6_frag.h | 3 ++- net/ipv4/inet_fragment.c | 8 +++++--- net/ipv4/ip_fragment.c | 3 ++- 4 files changed, 18 insertions(+), 7 deletions(-) diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h index 48cc5795ceda6bef86178fc1db0e1d6ee1dfd46d..63540be0fc34ac0f5270dd474bec96c65a5bdcbe 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 851029ecff13cb617d41b4043f039ae59e832b82..0a4779175a5238d8989a777ef8417223b6157679 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); diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c index 05cd198d7a6ba89ab9d12caf55108aba36c11fa0..341096807100cd65c4667031384ef59622771dac 100644 --- a/net/ipv4/inet_fragment.c +++ b/net/ipv4/inet_fragment.c @@ -235,9 +235,9 @@ void inet_frag_kill(struct inet_frag_queue *fq) /* The RCU read lock provides a memory barrier * guaranteeing that if fqdir->dead is false then * the hash table destruction will not start until - * after we unlock. Paired with inet_frags_exit_net(). + * after we unlock. Paired with fqdir_pre_exit(). */ - if (!fqdir->dead) { + if (!READ_ONCE(fqdir->dead)) { rhashtable_remove_fast(&fqdir->rhashtable, &fq->node, fqdir->f->rhash_params); refcount_dec(&fq->refcnt); @@ -352,9 +352,11 @@ static struct inet_frag_queue *inet_frag_create(struct fqdir *fqdir, /* TODO : call from rcu_read_lock() and no longer use refcount_inc_not_zero() */ struct inet_frag_queue *inet_frag_find(struct fqdir *fqdir, void *key) { + /* This pairs with WRITE_ONCE() in fqdir_pre_exit(). */ + long high_thresh = READ_ONCE(fqdir->high_thresh); struct inet_frag_queue *fq = NULL, *prev; - if (!fqdir->high_thresh || frag_mem_limit(fqdir) > fqdir->high_thresh) + if (!high_thresh || frag_mem_limit(fqdir) > high_thresh) return NULL; rcu_read_lock(); diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c index cfeb8890f94ee95b2246ba98beb338a33fc45d1d..fad803d2d711ef0d97f7150f0f710a35ac822946 100644 --- a/net/ipv4/ip_fragment.c +++ b/net/ipv4/ip_fragment.c @@ -144,7 +144,8 @@ static void ip_expire(struct timer_list *t) rcu_read_lock(); - if (qp->q.fqdir->dead) + /* Paired with WRITE_ONCE() in fqdir_pre_exit(). */ + if (READ_ONCE(qp->q.fqdir->dead)) goto out_rcu_unlock; spin_lock(&qp->q.lock); -- 2.34.1.575.g55b058a8bb-goog
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