[PATCH net-next] net: tcp_probe: adapt tbuf size for recent changes

[PATCH net-next] net: tcp_probe: adapt tbuf size for recent changes

[Daniel Borkmann]

With recent changes in tcp_probe module (e.g. f925d0a62d ("net: tcp_probe:
add IPv6 support")) we also need to take into account that tbuf needs to
be updated as format string will be further expanded. tbuf sits on the stack
in tcpprobe_read() function that is invoked when user space reads procfs
file /proc/net/tcpprobe, hence not fast path as in jtcp_rcv_established().
Having a size similarly as in sctp_probe module of 256 bytes is fully
sufficient for that, we need theoretical maximum of 252 bytes otherwise we
could get truncated.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
---
 net/ipv4/tcp_probe.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_probe.c b/net/ipv4/tcp_probe.c
index 622a437..1f6aa54 100644
--- a/net/ipv4/tcp_probe.c
+++ b/net/ipv4/tcp_probe.c
@@ -218,7 +218,7 @@ static ssize_t tcpprobe_read(struct file *file, char __user *buf,
 		return -EINVAL;
 
 	while (cnt < len) {
-		char tbuf[164];
+		char tbuf[256];
 		int width;
 
 		/* Wait for data in buffer */
-- 
1.7.11.7

Re: [PATCH net-next] net: tcp_probe: adapt tbuf size for recent changes

[David Miller]

From: Daniel Borkmann <dborkman@redhat.com>
Date: Tue,  3 Sep 2013 18:24:02 +0200

> With recent changes in tcp_probe module (e.g. f925d0a62d ("net: tcp_probe:
> add IPv6 support")) we also need to take into account that tbuf needs to
> be updated as format string will be further expanded. tbuf sits on the stack
> in tcpprobe_read() function that is invoked when user space reads procfs
> file /proc/net/tcpprobe, hence not fast path as in jtcp_rcv_established().
> Having a size similarly as in sctp_probe module of 256 bytes is fully
> sufficient for that, we need theoretical maximum of 252 bytes otherwise we
> could get truncated.
> 
> Signed-off-by: Daniel Borkmann <dborkman@redhat.com>

Applied.