[Devel] [PATCH RHEL7 COMMIT] ms/tun, bpf: fix suspicious RCU usage in tun_{attach, detach}_filter
Konstantin Khorenko
khorenko at virtuozzo.com
Wed Oct 23 17:41:05 MSK 2019
The commit is pushed to "branch-rh7-3.10.0-1062.1.2.vz7.114.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1062.1.2.vz7.114.9
------>
commit 8be3459fe1327d6eb63cf760c67c847f901d8f94
Author: Daniel Borkmann <daniel at iogearbox.net>
Date: Thu Mar 31 02:13:18 2016 +0200
ms/tun, bpf: fix suspicious RCU usage in tun_{attach, detach}_filter
[ Upstream commit 5a5abb1fa3b05dd6aa821525832644c1e7d2905f ]
Sasha Levin reported a suspicious rcu_dereference_protected() warning
found while fuzzing with trinity that is similar to this one:
[ 52.765684] net/core/filter.c:2262 suspicious rcu_dereference_protected() usage!
[ 52.765688] other info that might help us debug this:
[ 52.765695] rcu_scheduler_active = 1, debug_locks = 1
[ 52.765701] 1 lock held by a.out/1525:
[ 52.765704] #0: (rtnl_mutex){+.+.+.}, at: [<ffffffff816a64b7>] rtnl_lock+0x17/0x20
[ 52.765721] stack backtrace:
[ 52.765728] CPU: 1 PID: 1525 Comm: a.out Not tainted 4.5.0+ #264
[...]
[ 52.765768] Call Trace:
[ 52.765775] [<ffffffff813e488d>] dump_stack+0x85/0xc8
[ 52.765784] [<ffffffff810f2fa5>] lockdep_rcu_suspicious+0xd5/0x110
[ 52.765792] [<ffffffff816afdc2>] sk_detach_filter+0x82/0x90
[ 52.765801] [<ffffffffa0883425>] tun_detach_filter+0x35/0x90 [tun]
[ 52.765810] [<ffffffffa0884ed4>] __tun_chr_ioctl+0x354/0x1130 [tun]
[ 52.765818] [<ffffffff8136fed0>] ? selinux_file_ioctl+0x130/0x210
[ 52.765827] [<ffffffffa0885ce3>] tun_chr_ioctl+0x13/0x20 [tun]
[ 52.765834] [<ffffffff81260ea6>] do_vfs_ioctl+0x96/0x690
[ 52.765843] [<ffffffff81364af3>] ? security_file_ioctl+0x43/0x60
[ 52.765850] [<ffffffff81261519>] SyS_ioctl+0x79/0x90
[ 52.765858] [<ffffffff81003ba2>] do_syscall_64+0x62/0x140
[ 52.765866] [<ffffffff817d563f>] entry_SYSCALL64_slow_path+0x25/0x25
Same can be triggered with PROVE_RCU (+ PROVE_RCU_REPEATEDLY) enabled
from tun_attach_filter() when user space calls ioctl(tun_fd, TUN{ATTACH,
DETACH}FILTER, ...) for adding/removing a BPF filter on tap devices.
Since the fix in f91ff5b9ff52 ("net: sk_{detach|attach}_filter() rcu
fixes") sk_attach_filter()/sk_detach_filter() now dereferences the
filter with rcu_dereference_protected(), checking whether socket lock
is held in control path.
Since its introduction in 994051625981 ("tun: socket filter support"),
tap filters are managed under RTNL lock from __tun_chr_ioctl(). Thus the
sock_owned_by_user(sk) doesn't apply in this specific case and therefore
triggers the false positive.
Extend the BPF API with __sk_attach_filter()/__sk_detach_filter() pair
that is used by tap filters and pass in lockdep_rtnl_is_held() for the
rcu_dereference_protected() checks instead.
Reported-by: Sasha Levin <sasha.levin at oracle.com>
Signed-off-by: Daniel Borkmann <daniel at iogearbox.net>
Signed-off-by: David S. Miller <davem at davemloft.net>
[bwh: Backported to 3.16:
- Drop changes to sk_attach_bpf(), __sk_attach_prog()
- Adjust context]
Signed-off-by: Ben Hutchings <ben at decadent.org.uk>
https://jira.sw.ru/browse/PSBM-94755
(cherry picked from commit 71dbf84509be7ac7925e83da6fcc9e5e5dd02daa
from stable 3.16 kernel)
Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
drivers/net/tun.c | 8 +++++---
include/linux/filter.h | 3 +++
net/core/filter.c | 25 +++++++++++++++++--------
3 files changed, 25 insertions(+), 11 deletions(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index f54a881f9ac8..e65ded4d1d10 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -652,7 +652,8 @@ static int tun_attach(struct tun_struct *tun, struct file *file, bool skip_filte
/* Re-attach the filter to presist device */
if (!skip_filter && (tun->filter_attached == true)) {
- err = sk_attach_filter(&tun->fprog, tfile->socket.sk);
+ err = __sk_attach_filter(&tun->fprog, tfile->socket.sk,
+ lockdep_rtnl_is_held());
if (!err)
goto out;
}
@@ -2219,7 +2220,7 @@ 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);
+ __sk_detach_filter(tfile->socket.sk, lockdep_rtnl_is_held());
}
tun->filter_attached = false;
@@ -2232,7 +2233,8 @@ 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);
+ ret = __sk_attach_filter(&tun->fprog, tfile->socket.sk,
+ lockdep_rtnl_is_held());
if (ret) {
tun_detach_filter(tun, i);
return ret;
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 9f8aa2fe7f2f..452742d23581 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -599,7 +599,10 @@ extern int sk_unattached_filter_create(struct sk_filter **pfp,
struct sock_fprog *fprog);
extern void sk_unattached_filter_destroy(struct sk_filter *fp);
extern int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk);
+extern int __sk_attach_filter(struct sock_fprog *fprog, struct sock *sk,
+ bool locked);
extern int sk_detach_filter(struct sock *sk);
+extern int __sk_detach_filter(struct sock *sk, bool locked);
extern int sk_chk_filter(struct sock_filter *filter, unsigned int flen);
extern int sk_get_filter(struct sock *sk, struct sock_filter __user *filter, unsigned len);
extern void sk_decode_filter(struct sock_filter *filt, struct sock_filter *to);
diff --git a/net/core/filter.c b/net/core/filter.c
index afbef368f824..70e0c564aeaa 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -725,7 +725,8 @@ EXPORT_SYMBOL_GPL(sk_unattached_filter_destroy);
* 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)
+int __sk_attach_filter(struct sock_fprog *fprog, struct sock *sk,
+ bool locked)
{
struct sk_filter *fp, *old_fp;
unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
@@ -755,17 +756,21 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
return err;
}
- old_fp = rcu_dereference_protected(sk->sk_filter,
- sock_owned_by_user(sk));
+ old_fp = rcu_dereference_protected(sk->sk_filter, locked);
rcu_assign_pointer(sk->sk_filter, fp);
if (old_fp)
sk_filter_uncharge(sk, old_fp);
return 0;
}
-EXPORT_SYMBOL_GPL(sk_attach_filter);
+EXPORT_SYMBOL_GPL(__sk_attach_filter);
-int sk_detach_filter(struct sock *sk)
+int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
+{
+ return __sk_attach_filter(fprog, sk, sock_owned_by_user(sk));
+}
+
+int __sk_detach_filter(struct sock *sk, bool locked)
{
int ret = -ENOENT;
struct sk_filter *filter;
@@ -773,8 +778,7 @@ int sk_detach_filter(struct sock *sk)
if (sock_flag(sk, SOCK_FILTER_LOCKED))
return -EPERM;
- filter = rcu_dereference_protected(sk->sk_filter,
- sock_owned_by_user(sk));
+ filter = rcu_dereference_protected(sk->sk_filter, locked);
if (filter) {
RCU_INIT_POINTER(sk->sk_filter, NULL);
sk_filter_uncharge(sk, filter);
@@ -782,7 +786,12 @@ int sk_detach_filter(struct sock *sk)
}
return ret;
}
-EXPORT_SYMBOL_GPL(sk_detach_filter);
+EXPORT_SYMBOL_GPL(__sk_detach_filter);
+
+int sk_detach_filter(struct sock *sk)
+{
+ return __sk_detach_filter(sk, sock_owned_by_user(sk));
+}
void sk_decode_filter(struct sock_filter *filt, struct sock_filter *to)
{
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