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| author |   Eric Dumazet <edumazet@google.com> | 2019-05-17 17:17:22 -0700 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2019-06-15 18:47:31 -0700 |
| commit | 3b4929f65b0d8249f19a50245cd88ed1a2f78cff (patch) | |
| tree | 6f48603df7001f7048016a2e98573bf10044dd3e /include/linux/tcp.h | |
| parent | Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf (diff) | |
| download | linux-dev-3b4929f65b0d8249f19a50245cd88ed1a2f78cff.tar.xz linux-dev-3b4929f65b0d8249f19a50245cd88ed1a2f78cff.zip | |
tcp: limit payload size of sacked skbs
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>
Diffstat (limited to 'include/linux/tcp.h')
| -rw-r--r-- | include/linux/tcp.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 711361af9ce0..9a478a0cd3a2 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -484,4 +484,8 @@ 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 */ |