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Date: Tue, 23 Nov 2021 13:48:32 +0100
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: netdev@...r.kernel.org, David Ahern <dsahern@...il.com>,
Wei Wang <weiwan@...gle.com>,
David Miller <davem@...emloft.net>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: msizanoen1 <msizanoen@...labs.xyz>, stable@...r.kernel.org,
"Jason A . Donenfeld" <Jason@...c4.com>
Subject: [PATCH net] ipv6: fix memory leak in fib6_rule_suppress
From: msizanoen1 <msizanoen@...labs.xyz>
The kernel leaks memory when a `fib` rule is present in IPv6 nftables
firewall rules and a suppress_prefix rule is present in the IPv6 routing
rules (used by certain tools such as wg-quick). In such scenarios, every
incoming packet will leak an allocation in `ip6_dst_cache` slab cache.
After some hours of `bpftrace`-ing and source code reading, I tracked
down the issue to ca7a03c41753 ("ipv6: do not free rt if
FIB_LOOKUP_NOREF is set on suppress rule").
The problem with that change is that the generic `args->flags` always have
`FIB_LOOKUP_NOREF` set[1][2] but the IPv6-specific flag
`RT6_LOOKUP_F_DST_NOREF` might not be, leading to `fib6_rule_suppress` not
decreasing the refcount when needed.
How to reproduce:
- Add the following nftables rule to a prerouting chain:
meta nfproto ipv6 fib saddr . mark . iif oif missing drop
This can be done with:
sudo nft create table inet test
sudo nft create chain inet test test_chain '{ type filter hook prerouting priority filter + 10; policy accept; }'
sudo nft add rule inet test test_chain meta nfproto ipv6 fib saddr . mark . iif oif missing drop
- Run:
sudo ip -6 rule add table main suppress_prefixlength 0
- Watch `sudo slabtop -o | grep ip6_dst_cache` to see memory usage increase
with every incoming ipv6 packet.
This patch exposes the protocol-specific flags to the protocol
specific `suppress` function, and check the protocol-specific `flags`
argument for RT6_LOOKUP_F_DST_NOREF instead of the generic
FIB_LOOKUP_NOREF when decreasing the refcount, like this.
[1]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L71
[2]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L99
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215105
Fixes: ca7a03c41753 ("ipv6: do not free rt if FIB_LOOKUP_NOREF is set on suppress rule")
Cc: stable@...r.kernel.org
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
The original author of this commit and commit message is anonymous and
is therefore unable to sign off on it. Greg suggested that I do the sign
off, extracting it from the bugzilla entry above, and post it properly.
The patch "seems to work" on first glance, but I haven't looked deeply
at it yet and therefore it doesn't have my Reviewed-by, even though I'm
submitting this patch on the author's behalf. And it should probably get
a good look from the v6 fib folks. The original author should be on this
thread to address issues that come off, and I'll shephard additional
versions that he has.
include/net/fib_rules.h | 4 +++-
net/core/fib_rules.c | 2 +-
net/ipv4/fib_rules.c | 1 +
net/ipv6/fib6_rules.c | 4 ++--
4 files changed, 7 insertions(+), 4 deletions(-)
diff --git a/include/net/fib_rules.h b/include/net/fib_rules.h
index 4b10676c69d1..bd07484ab9dd 100644
--- a/include/net/fib_rules.h
+++ b/include/net/fib_rules.h
@@ -69,7 +69,7 @@ struct fib_rules_ops {
int (*action)(struct fib_rule *,
struct flowi *, int,
struct fib_lookup_arg *);
- bool (*suppress)(struct fib_rule *,
+ bool (*suppress)(struct fib_rule *, int,
struct fib_lookup_arg *);
int (*match)(struct fib_rule *,
struct flowi *, int);
@@ -218,7 +218,9 @@ INDIRECT_CALLABLE_DECLARE(int fib4_rule_action(struct fib_rule *rule,
struct fib_lookup_arg *arg));
INDIRECT_CALLABLE_DECLARE(bool fib6_rule_suppress(struct fib_rule *rule,
+ int flags,
struct fib_lookup_arg *arg));
INDIRECT_CALLABLE_DECLARE(bool fib4_rule_suppress(struct fib_rule *rule,
+ int flags,
struct fib_lookup_arg *arg));
#endif
diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 79df7cd9dbc1..1bb567a3b329 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -323,7 +323,7 @@ int fib_rules_lookup(struct fib_rules_ops *ops, struct flowi *fl,
if (!err && ops->suppress && INDIRECT_CALL_MT(ops->suppress,
fib6_rule_suppress,
fib4_rule_suppress,
- rule, arg))
+ rule, flags, arg))
continue;
if (err != -EAGAIN) {
diff --git a/net/ipv4/fib_rules.c b/net/ipv4/fib_rules.c
index ce54a30c2ef1..364ad3446b2f 100644
--- a/net/ipv4/fib_rules.c
+++ b/net/ipv4/fib_rules.c
@@ -141,6 +141,7 @@ INDIRECT_CALLABLE_SCOPE int fib4_rule_action(struct fib_rule *rule,
}
INDIRECT_CALLABLE_SCOPE bool fib4_rule_suppress(struct fib_rule *rule,
+ int flags,
struct fib_lookup_arg *arg)
{
struct fib_result *result = (struct fib_result *) arg->result;
diff --git a/net/ipv6/fib6_rules.c b/net/ipv6/fib6_rules.c
index 40f3e4f9f33a..dcedfe29d9d9 100644
--- a/net/ipv6/fib6_rules.c
+++ b/net/ipv6/fib6_rules.c
@@ -267,6 +267,7 @@ INDIRECT_CALLABLE_SCOPE int fib6_rule_action(struct fib_rule *rule,
}
INDIRECT_CALLABLE_SCOPE bool fib6_rule_suppress(struct fib_rule *rule,
+ int flags,
struct fib_lookup_arg *arg)
{
struct fib6_result *res = arg->result;
@@ -294,8 +295,7 @@ INDIRECT_CALLABLE_SCOPE bool fib6_rule_suppress(struct fib_rule *rule,
return false;
suppress_route:
- if (!(arg->flags & FIB_LOOKUP_NOREF))
- ip6_rt_put(rt);
+ ip6_rt_put_flags(rt, flags);
return true;
}
--
2.34.0
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