[PATCH net] sock, diag: fix panic in sock_diag_put_filterinfo

[PATCH net] sock, diag: fix panic in sock_diag_put_filterinfo

[Daniel Borkmann]

diag socket's sock_diag_put_filterinfo() dumps classic BPF programs
upon request to user space (ss -0 -b). However, native eBPF programs
attached to sockets (SO_ATTACH_BPF) cannot be dumped with this method:

Their orig_prog is always NULL. However, sock_diag_put_filterinfo()
unconditionally tries to access its filter length resp. wants to copy
the filter insns from there. Internal cBPF to eBPF transformations
attached to sockets don't have this issue, as orig_prog state is kept.

It's currently only used by packet sockets. If we would want to add
native eBPF support in the future, this needs to be done through
a different attribute than PACKET_DIAG_FILTER to not confuse possible
user space disassemblers that work on diag data.

Fixes: 89aa075832b0 ("net: sock: allow eBPF programs to be attached to sockets")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 net/core/sock_diag.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/sock_diag.c b/net/core/sock_diag.c
index d79866c..817622f 100644
--- a/net/core/sock_diag.c
+++ b/net/core/sock_diag.c
@@ -90,6 +90,9 @@ int sock_diag_put_filterinfo(bool may_report_filterinfo, struct sock *sk,
 		goto out;
 
 	fprog = filter->prog->orig_prog;
+	if (!fprog)
+		goto out;
+
 	flen = bpf_classic_proglen(fprog);
 
 	attr = nla_reserve(skb, attrtype, flen);
-- 
1.9.3

Re: [PATCH net] sock, diag: fix panic in sock_diag_put_filterinfo

[Nicolas Dichtel]

Le 02/09/2015 14:00, Daniel Borkmann a écrit :
> diag socket's sock_diag_put_filterinfo() dumps classic BPF programs
> upon request to user space (ss -0 -b). However, native eBPF programs
> attached to sockets (SO_ATTACH_BPF) cannot be dumped with this method:
>
> Their orig_prog is always NULL. However, sock_diag_put_filterinfo()
> unconditionally tries to access its filter length resp. wants to copy
> the filter insns from there. Internal cBPF to eBPF transformations
> attached to sockets don't have this issue, as orig_prog state is kept.
>
> It's currently only used by packet sockets. If we would want to add
> native eBPF support in the future, this needs to be done through
> a different attribute than PACKET_DIAG_FILTER to not confuse possible
> user space disassemblers that work on diag data.
>
> Fixes: 89aa075832b0 ("net: sock: allow eBPF programs to be attached to sockets")
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>

Re: [PATCH net] sock, diag: fix panic in sock_diag_put_filterinfo

[Alexei Starovoitov]

On 9/2/15 5:00 AM, Daniel Borkmann wrote:
> diag socket's sock_diag_put_filterinfo() dumps classic BPF programs
> upon request to user space (ss -0 -b). However, native eBPF programs
> attached to sockets (SO_ATTACH_BPF) cannot be dumped with this method:
...
> Fixes: 89aa075832b0 ("net: sock: allow eBPF programs to be attached to sockets")
> Signed-off-by: Daniel Borkmann<daniel@iogearbox.net>

good catch. thanks
Acked-by: Alexei Starovoitov <ast@plumgrid.com>

Re: [PATCH net] sock, diag: fix panic in sock_diag_put_filterinfo

[David Miller]

From: Daniel Borkmann <daniel@iogearbox.net>
Date: Wed,  2 Sep 2015 14:00:36 +0200

> diag socket's sock_diag_put_filterinfo() dumps classic BPF programs
> upon request to user space (ss -0 -b). However, native eBPF programs
> attached to sockets (SO_ATTACH_BPF) cannot be dumped with this method:
> 
> Their orig_prog is always NULL. However, sock_diag_put_filterinfo()
> unconditionally tries to access its filter length resp. wants to copy
> the filter insns from there. Internal cBPF to eBPF transformations
> attached to sockets don't have this issue, as orig_prog state is kept.
> 
> It's currently only used by packet sockets. If we would want to add
> native eBPF support in the future, this needs to be done through
> a different attribute than PACKET_DIAG_FILTER to not confuse possible
> user space disassemblers that work on diag data.
> 
> Fixes: 89aa075832b0 ("net: sock: allow eBPF programs to be attached to sockets")
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Applied and queued up for -stable, thanks.