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ipv4: tcp_input: fix stack out of bounds when parsing TCP options.

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The TCP option parsing routines in tcp_parse_options function could
read one byte out of the buffer of the TCP options.

1         while (length > 0) {
2                 int opcode = *ptr++;
3                 int opsize;
4
5                 switch (opcode) {
6                 case TCPOPT_EOL:
7                         return;
8                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
9                         length--;
10                        continue;
11                default:
12                        opsize = *ptr++; //out of bound access

If length = 1, then there is an access in line2.
And another access is occurred in line 12.
This would lead to out-of-bound access.

Therefore, in the patch we check that the available data length is
larger enough to pase both TCP option code and size.

Signed-off-by: Young Xiao <92siuyang@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Young Xiao 2019-05-29 16:10:59 +08:00 committed by David S. Miller
parent 62851d71e7
commit 9609dad263
1 changed files with 2 additions and 0 deletions
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2
net/ipv4/tcp_input.c
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@ -3791,6 +3791,8 @@ void tcp_parse_options(const struct net *net,
length--;
continue;
default:
if (length < 2)
return;
opsize = *ptr++;
if (opsize < 2) /* "silly options" */
return;