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tcp: correct read of TFO keys on big endian systems

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When TFO keys are read back on big endian systems either via the global
sysctl interface or via getsockopt() using TCP_FASTOPEN_KEY, the values
don't match what was written.

For example, on s390x:

# echo "1-2-3-4" > /proc/sys/net/ipv4/tcp_fastopen_key
# cat /proc/sys/net/ipv4/tcp_fastopen_key
02000000-01000000-04000000-03000000

Instead of:

# cat /proc/sys/net/ipv4/tcp_fastopen_key
00000001-00000002-00000003-00000004

Fix this by converting to the correct endianness on read. This was
reported by Colin Ian King when running the 'tcp_fastopen_backup_key' net
selftest on s390x, which depends on the read value matching what was
written. I've confirmed that the test now passes on big and little endian
systems.

Signed-off-by: Jason Baron <jbaron@akamai.com>
Fixes: 438ac88009 ("net: fastopen: robustness and endianness fixes for SipHash")
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Eric Dumazet <edumazet@google.com>
Reported-and-tested-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jason Baron
2020-08-10 13:38:39 -04:00
committed by David S. Miller
parent 56e287b3da
commit f19008e676
4 changed files with 33 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
net/ipv4/tcp.c
View File

@@ -3685,22 +3685,14 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
return 0;
case TCP_FASTOPEN_KEY: {
__u8 key[TCP_FASTOPEN_KEY_BUF_LENGTH];
struct tcp_fastopen_context *ctx;
unsigned int key_len = 0;
u64 key[TCP_FASTOPEN_KEY_BUF_LENGTH / sizeof(u64)];
unsigned int key_len;
if (get_user(len, optlen))
return -EFAULT;
rcu_read_lock();
ctx = rcu_dereference(icsk->icsk_accept_queue.fastopenq.ctx);
if (ctx) {
key_len = tcp_fastopen_context_len(ctx) *
TCP_FASTOPEN_KEY_LENGTH;
memcpy(&key[0], &ctx->key[0], key_len);
}
rcu_read_unlock();
key_len = tcp_fastopen_get_cipher(net, icsk, key) *
TCP_FASTOPEN_KEY_LENGTH;
len = min_t(unsigned int, len, key_len);
if (put_user(len, optlen))
return -EFAULT;