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tun: use socket locks for sk_{attach,detatch}_filter 

This reverts commit 5a5abb1fa3 ("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@iogearbox.net>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Hannes Frederic Sowa 2016-04-05 17:10:16 +02:00 committed by David S. Miller
parent 1e1d04e678
commit 8ced425ee6
3 changed files with 22 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
drivers/net/tun.c
View File

@ -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;

4
include/linux/filter.h
View File

@ -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);

35
net/core/filter.c
View File

@ -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;