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Date: Tue, 5 Apr 2016 17:10:16 +0200
From: Hannes Frederic Sowa <hannes@...essinduktion.org>
To: netdev@...r.kernel.org
Cc: daniel@...earbox.net
Subject: [PATCH net-next 3/3] tun: use socket locks for sk_{attach,detatch}_filter
This reverts commit 5a5abb1fa3b05dd ("tun, bpf: fix suspicious RCU usage
in tun_{attach, detach}_filter") and replaces it to use lock_sock around
sk_{attach,detach}_filter. The checks inside filter.c are updated with
lockdep_sock_is_held to check for proper socket locks.
It keeps the code cleaner by ensuring that only one lock governs the
socket filter instead of two independent locks.
Cc: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
---
drivers/net/tun.c | 14 +++++++++-----
include/linux/filter.h | 4 ----
net/core/filter.c | 35 +++++++++++++----------------------
3 files changed, 22 insertions(+), 31 deletions(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 9abc36bf77eae3..64bc143eddd983 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -622,8 +622,9 @@ static int tun_attach(struct tun_struct *tun, struct file *file, bool skip_filte
/* Re-attach the filter to persist device */
if (!skip_filter && (tun->filter_attached == true)) {
- err = __sk_attach_filter(&tun->fprog, tfile->socket.sk,
- lockdep_rtnl_is_held());
+ lock_sock(tfile->socket.sk);
+ err = sk_attach_filter(&tun->fprog, tfile->socket.sk);
+ release_sock(tfile->socket.sk);
if (!err)
goto out;
}
@@ -1824,7 +1825,9 @@ static void tun_detach_filter(struct tun_struct *tun, int n)
for (i = 0; i < n; i++) {
tfile = rtnl_dereference(tun->tfiles[i]);
- __sk_detach_filter(tfile->socket.sk, lockdep_rtnl_is_held());
+ lock_sock(tfile->socket.sk);
+ sk_detach_filter(tfile->socket.sk);
+ release_sock(tfile->socket.sk);
}
tun->filter_attached = false;
@@ -1837,8 +1840,9 @@ static int tun_attach_filter(struct tun_struct *tun)
for (i = 0; i < tun->numqueues; i++) {
tfile = rtnl_dereference(tun->tfiles[i]);
- ret = __sk_attach_filter(&tun->fprog, tfile->socket.sk,
- lockdep_rtnl_is_held());
+ lock_sock(tfile->socket.sk);
+ ret = sk_attach_filter(&tun->fprog, tfile->socket.sk);
+ release_sock(tfile->socket.sk);
if (ret) {
tun_detach_filter(tun, i);
return ret;
diff --git a/include/linux/filter.h b/include/linux/filter.h
index a51a5361695fbf..43aa1f8855c7ff 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -465,14 +465,10 @@ int bpf_prog_create_from_user(struct bpf_prog **pfp, struct sock_fprog *fprog,
void bpf_prog_destroy(struct bpf_prog *fp);
int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk);
-int __sk_attach_filter(struct sock_fprog *fprog, struct sock *sk,
- bool locked);
int sk_attach_bpf(u32 ufd, struct sock *sk);
int sk_reuseport_attach_filter(struct sock_fprog *fprog, struct sock *sk);
int sk_reuseport_attach_bpf(u32 ufd, struct sock *sk);
int sk_detach_filter(struct sock *sk);
-int __sk_detach_filter(struct sock *sk, bool locked);
-
int sk_get_filter(struct sock *sk, struct sock_filter __user *filter,
unsigned int len);
diff --git a/net/core/filter.c b/net/core/filter.c
index ca7f832b29802d..e8486ba601eae7 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1149,8 +1149,7 @@ void bpf_prog_destroy(struct bpf_prog *fp)
}
EXPORT_SYMBOL_GPL(bpf_prog_destroy);
-static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk,
- bool locked)
+static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk)
{
struct sk_filter *fp, *old_fp;
@@ -1166,8 +1165,10 @@ static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk,
return -ENOMEM;
}
- old_fp = rcu_dereference_protected(sk->sk_filter, locked);
+ old_fp = rcu_dereference_protected(sk->sk_filter,
+ lockdep_sock_is_held(sk));
rcu_assign_pointer(sk->sk_filter, fp);
+
if (old_fp)
sk_filter_uncharge(sk, old_fp);
@@ -1246,8 +1247,7 @@ struct bpf_prog *__get_filter(struct sock_fprog *fprog, struct sock *sk)
* occurs or there is insufficient memory for the filter a negative
* errno code is returned. On success the return is zero.
*/
-int __sk_attach_filter(struct sock_fprog *fprog, struct sock *sk,
- bool locked)
+int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
{
struct bpf_prog *prog = __get_filter(fprog, sk);
int err;
@@ -1255,7 +1255,7 @@ int __sk_attach_filter(struct sock_fprog *fprog, struct sock *sk,
if (IS_ERR(prog))
return PTR_ERR(prog);
- err = __sk_attach_prog(prog, sk, locked);
+ err = __sk_attach_prog(prog, sk);
if (err < 0) {
__bpf_prog_release(prog);
return err;
@@ -1263,12 +1263,7 @@ int __sk_attach_filter(struct sock_fprog *fprog, struct sock *sk,
return 0;
}
-EXPORT_SYMBOL_GPL(__sk_attach_filter);
-
-int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
-{
- return __sk_attach_filter(fprog, sk, sock_owned_by_user(sk));
-}
+EXPORT_SYMBOL_GPL(sk_attach_filter);
int sk_reuseport_attach_filter(struct sock_fprog *fprog, struct sock *sk)
{
@@ -1314,7 +1309,7 @@ int sk_attach_bpf(u32 ufd, struct sock *sk)
if (IS_ERR(prog))
return PTR_ERR(prog);
- err = __sk_attach_prog(prog, sk, sock_owned_by_user(sk));
+ err = __sk_attach_prog(prog, sk);
if (err < 0) {
bpf_prog_put(prog);
return err;
@@ -2255,7 +2250,7 @@ static int __init register_sk_filter_ops(void)
}
late_initcall(register_sk_filter_ops);
-int __sk_detach_filter(struct sock *sk, bool locked)
+int sk_detach_filter(struct sock *sk)
{
int ret = -ENOENT;
struct sk_filter *filter;
@@ -2263,7 +2258,8 @@ int __sk_detach_filter(struct sock *sk, bool locked)
if (sock_flag(sk, SOCK_FILTER_LOCKED))
return -EPERM;
- filter = rcu_dereference_protected(sk->sk_filter, locked);
+ filter = rcu_dereference_protected(sk->sk_filter,
+ lockdep_sock_is_held(sk));
if (filter) {
RCU_INIT_POINTER(sk->sk_filter, NULL);
sk_filter_uncharge(sk, filter);
@@ -2272,12 +2268,7 @@ int __sk_detach_filter(struct sock *sk, bool locked)
return ret;
}
-EXPORT_SYMBOL_GPL(__sk_detach_filter);
-
-int sk_detach_filter(struct sock *sk)
-{
- return __sk_detach_filter(sk, sock_owned_by_user(sk));
-}
+EXPORT_SYMBOL_GPL(sk_detach_filter);
int sk_get_filter(struct sock *sk, struct sock_filter __user *ubuf,
unsigned int len)
@@ -2288,7 +2279,7 @@ int sk_get_filter(struct sock *sk, struct sock_filter __user *ubuf,
lock_sock(sk);
filter = rcu_dereference_protected(sk->sk_filter,
- sock_owned_by_user(sk));
+ lockdep_sock_is_held(sk));
if (!filter)
goto out;
--
2.5.5
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