diff options
| author | Eric Dumazet <edumazet@google.com> | 2023-05-24 14:14:56 +0000 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2023-05-25 21:02:29 -0700 |
| commit | 31642e7089df8fd3f54ca7843f7ee2952978cad1 (patch) | |
| tree | e0c1b0669ada69fc25856ac95eeec8bf29c4b4f6 /net/netrom | |
| parent | ffb3322181d9e8db880202e4f00991764a35d812 (diff) | |
netrom: fix info-leak in nr_write_internal()
Simon Kapadia reported the following issue:
<quote>
The Online Amateur Radio Community (OARC) has recently been experimenting
with building a nationwide packet network in the UK.
As part of our experimentation, we have been testing out packet on 300bps HF,
and playing with net/rom. For HF packet at this baud rate you really need
to make sure that your MTU is relatively low; AX.25 suggests a PACLEN of 60,
and a net/rom PACLEN of 40 to go with that.
However the Linux net/rom support didn't work with a low PACLEN;
the mkiss module would truncate packets if you set the PACLEN below about 200 or so, e.g.:
Apr 19 14:00:51 radio kernel: [12985.747310] mkiss: ax1: truncating oversized transmit packet!
This didn't make any sense to me (if the packets are smaller why would they
be truncated?) so I started investigating.
I looked at the packets using ethereal, and found that many were just huge
compared to what I would expect.
A simple net/rom connection request packet had the request and then a bunch
of what appeared to be random data following it:
</quote>
Simon provided a patch that I slightly revised:
Not only we must not use skb_tailroom(), we also do
not want to count NR_NETWORK_LEN twice.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Co-Developed-by: Simon Kapadia <szymon@kapadia.pl>
Signed-off-by: Simon Kapadia <szymon@kapadia.pl>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Simon Kapadia <szymon@kapadia.pl>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230524141456.1045467-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/netrom')
| -rw-r--r-- | net/netrom/nr_subr.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/net/netrom/nr_subr.c b/net/netrom/nr_subr.c index 3f99b432ea70..e2d2af924cff 100644 --- a/net/netrom/nr_subr.c +++ b/net/netrom/nr_subr.c @@ -123,7 +123,7 @@ void nr_write_internal(struct sock *sk, int frametype) unsigned char *dptr; int len, timeout; - len = NR_NETWORK_LEN + NR_TRANSPORT_LEN; + len = NR_TRANSPORT_LEN; switch (frametype & 0x0F) { case NR_CONNREQ: @@ -141,7 +141,8 @@ void nr_write_internal(struct sock *sk, int frametype) return; } - if ((skb = alloc_skb(len, GFP_ATOMIC)) == NULL) + skb = alloc_skb(NR_NETWORK_LEN + len, GFP_ATOMIC); + if (!skb) return; /* @@ -149,7 +150,7 @@ void nr_write_internal(struct sock *sk, int frametype) */ skb_reserve(skb, NR_NETWORK_LEN); - dptr = skb_put(skb, skb_tailroom(skb)); + dptr = skb_put(skb, len); switch (frametype & 0x0F) { case NR_CONNREQ: |