diff options
| author | Eric Dumazet <edumazet@google.com> | 2019-05-17 17:17:22 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-06-17 19:51:56 +0200 |
| commit | c09be31461ed140976c60a87364415454a2c3d42 (patch) | |
| tree | 058ef7ea0b3cc01e07cad55f8fe3b50e498ac2a8 /include | |
| parent | 7aa823a959e1f50c0dab9e01c1940235eccc04cc (diff) | |
tcp: limit payload size of sacked skbs
commit 3b4929f65b0d8249f19a50245cd88ed1a2f78cff upstream.
Jonathan Looney reported that TCP can trigger the following crash
in tcp_shifted_skb() :
BUG_ON(tcp_skb_pcount(skb) < pcount);
This can happen if the remote peer has advertized the smallest
MSS that linux TCP accepts : 48
An skb can hold 17 fragments, and each fragment can hold 32KB
on x86, or 64KB on PowerPC.
This means that the 16bit witdh of TCP_SKB_CB(skb)->tcp_gso_segs
can overflow.
Note that tcp_sendmsg() builds skbs with less than 64KB
of payload, so this problem needs SACK to be enabled.
SACK blocks allow TCP to coalesce multiple skbs in the retransmit
queue, thus filling the 17 fragments to maximal capacity.
CVE-2019-11477 -- u16 overflow of TCP_SKB_CB(skb)->tcp_gso_segs
Fixes: 832d11c5cd07 ("tcp: Try to restore large SKBs while SACK processing")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Jonathan Looney <jtl@netflix.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Bruce Curtis <brucec@netflix.com>
Cc: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/tcp.h | 4 | ||||
| -rw-r--r-- | include/net/tcp.h | 2 |
2 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/tcp.h b/include/linux/tcp.h index d2c8f280e48f..4374196b98ea 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -485,4 +485,8 @@ static inline u16 tcp_mss_clamp(const struct tcp_sock *tp, u16 mss) return (user_mss && user_mss < mss) ? user_mss : mss; } + +int tcp_skb_shift(struct sk_buff *to, struct sk_buff *from, int pcount, + int shiftlen); + #endif /* _LINUX_TCP_H */ diff --git a/include/net/tcp.h b/include/net/tcp.h index 770917d0caa7..e75661f92daa 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -55,6 +55,8 @@ void tcp_time_wait(struct sock *sk, int state, int timeo); #define MAX_TCP_HEADER (128 + MAX_HEADER) #define MAX_TCP_OPTION_SPACE 40 +#define TCP_MIN_SND_MSS 48 +#define TCP_MIN_GSO_SIZE (TCP_MIN_SND_MSS - MAX_TCP_OPTION_SPACE) /* * Never offer a window over 32767 without using window scaling. Some |