selftests: mptcp: diag: fix stack buffer overflow in get_subflow_info()

get_subflow_info() parses the subflow address string with:

	char saddr[64], daddr[64];

	ret = sscanf(subflow_addrs, "%[^:]:%d %[^:]:%d",
		     saddr, &sport, daddr, &dport);

The subflow_addrs buffer holds up to 1024 bytes and is taken directly
from the command line ("-c" argument). The "%[^:]" conversions have no
maximum field width, so if the address substring before the ':' exceeds
63 bytes, sscanf() writes past the end of the 64-byte saddr/daddr stack
buffers. This overflows the stack, corrupting adjacent stack data such
as the saved return address, and can crash the tool or lead to
out-of-bounds writes controlled by user-supplied input.

Bound both string conversions to the destination buffer size by adding
an explicit maximum field width of 63 (leaving room for the terminating
NUL), so at most 63 bytes are written into each 64-byte buffer:

	ret = sscanf(subflow_addrs, "%63[^:]:%d %63[^:]:%d",
		     saddr, &sport, daddr, &dport);

The subflow address can be passed in argument, so fixing this is helpful
when the tool is manually used.

Reviewed-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Jiangshan Yi <yijiangshan@kylinos.cn>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260812-net-next-mptcp-misc-feat-7-3-v1-11-1905a818f6cb@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions