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author | Daniel Borkmann <daniel@iogearbox.net> | 2016-03-31 02:13:18 +0200 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2016-04-01 14:33:46 -0400 |
commit | 5a5abb1fa3b05dd6aa821525832644c1e7d2905f (patch) | |
tree | f6b9a82511558e0c9d456194db3fc702ca7411da /net | |
parent | 79f4223257bfef52b0a26d0d7ad4019e764be6ce (diff) | |
download | blackbird-op-linux-5a5abb1fa3b05dd6aa821525832644c1e7d2905f.tar.gz blackbird-op-linux-5a5abb1fa3b05dd6aa821525832644c1e7d2905f.zip |
tun, bpf: fix suspicious RCU usage in tun_{attach, detach}_filter
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@oracle.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r-- | net/core/filter.c | 33 |
1 files changed, 21 insertions, 12 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index 4b81b71171b4..ca7f832b2980 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1149,7 +1149,8 @@ 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) +static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk, + bool locked) { struct sk_filter *fp, *old_fp; @@ -1165,10 +1166,8 @@ static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk) return -ENOMEM; } - 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); @@ -1247,7 +1246,8 @@ 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) +int __sk_attach_filter(struct sock_fprog *fprog, struct sock *sk, + bool locked) { 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); + err = __sk_attach_prog(prog, sk, locked); if (err < 0) { __bpf_prog_release(prog); return err; @@ -1263,7 +1263,12 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk) return 0; } -EXPORT_SYMBOL_GPL(sk_attach_filter); +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)); +} int sk_reuseport_attach_filter(struct sock_fprog *fprog, struct sock *sk) { @@ -1309,7 +1314,7 @@ int sk_attach_bpf(u32 ufd, struct sock *sk) if (IS_ERR(prog)) return PTR_ERR(prog); - err = __sk_attach_prog(prog, sk); + err = __sk_attach_prog(prog, sk, sock_owned_by_user(sk)); if (err < 0) { bpf_prog_put(prog); return err; @@ -2250,7 +2255,7 @@ static int __init register_sk_filter_ops(void) } late_initcall(register_sk_filter_ops); -int sk_detach_filter(struct sock *sk) +int __sk_detach_filter(struct sock *sk, bool locked) { int ret = -ENOENT; struct sk_filter *filter; @@ -2258,8 +2263,7 @@ 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); @@ -2268,7 +2272,12 @@ 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)); +} int sk_get_filter(struct sock *sk, struct sock_filter __user *ubuf, unsigned int len) |