diff options
| author | Will Deacon <will@kernel.org> | 2020-04-03 16:13:21 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2020-04-06 10:00:43 -0700 |
| commit | bee348907d19d654e8524d3a946dcd25b693aa7e (patch) | |
| tree | 1bbeb3d08325c50743147353e64dfced2668748a /drivers/net/tun.c | |
| parent | 0452800f6db4ed0a42ffb15867c0acfd68829f6a (diff) | |
tun: Don't put_page() for all negative return values from XDP program
When an XDP program is installed, tun_build_skb() grabs a reference to
the current page fragment page if the program returns XDP_REDIRECT or
XDP_TX. However, since tun_xdp_act() passes through negative return
values from the XDP program, it is possible to trigger the error path by
mistake and accidentally drop a reference to the fragments page without
taking one, leading to a spurious free. This is believed to be the cause
of some KASAN use-after-free reports from syzbot [1], although without a
reproducer it is not possible to confirm whether this patch fixes the
problem.
Ensure that we only drop a reference to the fragments page if the XDP
transmit or redirect operations actually fail.
[1] https://syzkaller.appspot.com/bug?id=e76a6af1be4acd727ff6bbca669833f98cbf5d95
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
CC: Eric Dumazet <edumazet@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Fixes: 8ae1aff0b331 ("tuntap: split out XDP logic")
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/tun.c')
| -rw-r--r-- | drivers/net/tun.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 228fe449dc6d..07476c6510f2 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1678,8 +1678,12 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun, alloc_frag->offset += buflen; } err = tun_xdp_act(tun, xdp_prog, &xdp, act); - if (err < 0) - goto err_xdp; + if (err < 0) { + if (act == XDP_REDIRECT || act == XDP_TX) + put_page(alloc_frag->page); + goto out; + } + if (err == XDP_REDIRECT) xdp_do_flush(); if (err != XDP_PASS) @@ -1693,8 +1697,6 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun, return __tun_build_skb(tfile, alloc_frag, buf, buflen, len, pad); -err_xdp: - put_page(alloc_frag->page); out: rcu_read_unlock(); local_bh_enable(); |