[PATCH 5.19 140/207] netfilter: nf_ct_ftp: fix deadlock when nat rewrite is needed

Greg Kroah-Hartman
2022-09-26T11:56:24Z

From: Florian Westphal <fw@strlen.de>

[ Upstream commit d25088932227680988a6b794221e031a7232f137 ]

We can't use ct->lock, this is already used by the seqadj internals.
When using ftp helper + nat, seqadj will attempt to acquire ct->lock
again.

Revert back to a global lock for now.

Fixes: c783a29c7e59 ("netfilter: nf_ct_ftp: prefer skb_linearize")
Reported-by: Bruno de Paula Larini <bruno.larini@riosoft.com.br>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nf_conntrack_ftp.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_conntrack_ftp.c b/net/netfilter/nf_conntrack_ftp.c
index 0d9332e9cf71..617f744a2e3a 100644
--- a/net/netfilter/nf_conntrack_ftp.c
+++ b/net/netfilter/nf_conntrack_ftp.c
@@ -33,6 +33,7 @@ MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
MODULE_DESCRIPTION("ftp connection tracking helper");
MODULE_ALIAS("ip_conntrack_ftp");
MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
+static DEFINE_SPINLOCK(nf_ftp_lock);

#define MAX_PORTS 8
static u_int16_t ports[MAX_PORTS];
@@ -409,7 +410,8 @@ static int help(struct sk_buff *skb,
}
datalen = skb->len - dataoff;

- spin_lock_bh(&ct->lock);
+ /* seqadj (nat) uses ct->lock internally, nf_nat_ftp would cause deadlock */
+ spin_lock_bh(&nf_ftp_lock);
fb_ptr = skb->data + dataoff;

ends_in_nl = (fb_ptr[datalen - 1] == '\n');
@@ -538,7 +540,7 @@ static int help(struct sk_buff *skb,
if (ends_in_nl)
update_nl_seq(ct, seq, ct_ftp_info, dir, skb);
out:
- spin_unlock_bh(&ct->lock);
+ spin_unlock_bh(&nf_ftp_lock);
return ret;
}

--
2.35.1