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| author | Daniel Borkmann <daniel@iogearbox.net> | 2016-03-31 03:13:18 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-04-01 21:33:46 +0300 |
| commit | 5a5abb1fa3b05dd6aa821525832644c1e7d2905f (patch) | |
| tree | f6b9a82511558e0c9d456194db3fc702ca7411da /include | |
| parent | 79f4223257bfef52b0a26d0d7ad4019e764be6ce (diff) | |
| download | linux-5a5abb1fa3b05dd6aa821525832644c1e7d2905f.tar.xz | |
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 'include')
| -rw-r--r-- | include/linux/filter.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/filter.h b/include/linux/filter.h index 43aa1f8855c7..a51a5361695f 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -465,10 +465,14 @@ 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); |