From 8a11ff0948b5ad09b71896b7ccc850625f9878d1 Mon Sep 17 00:00:00 2001 From: Junrui Luo Date: Thu, 4 Dec 2025 21:30:47 +0800 Subject: [PATCH] caif: fix integer underflow in cffrml_receive() The cffrml_receive() function extracts a length field from the packet header and, when FCS is disabled, subtracts 2 from this length without validating that len >= 2. If an attacker sends a malicious packet with a length field of 0 or 1 to an interface with FCS disabled, the subtraction causes an integer underflow. This can lead to memory exhaustion and kernel instability, potential information disclosure if padding contains uninitialized kernel memory. Fix this by validating that len >= 2 before performing the subtraction. Reported-by: Yuhao Jiang Reported-by: Junrui Luo Fixes: b482cd2053e3 ("net-caif: add CAIF core protocol stack") Signed-off-by: Junrui Luo Reviewed-by: Simon Horman Link: https://patch.msgid.link/SYBPR01MB7881511122BAFEA8212A1608AFA6A@SYBPR01MB7881.ausprd01.prod.outlook.com Signed-off-by: Jakub Kicinski --- net/caif/cffrml.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/net/caif/cffrml.c b/net/caif/cffrml.c index 6651a8dc62e0..d4d63586053a 100644 --- a/net/caif/cffrml.c +++ b/net/caif/cffrml.c @@ -92,8 +92,15 @@ static int cffrml_receive(struct cflayer *layr, struct cfpkt *pkt) len = le16_to_cpu(tmp); /* Subtract for FCS on length if FCS is not used. */ - if (!this->dofcs) + if (!this->dofcs) { + if (len < 2) { + ++cffrml_rcv_error; + pr_err("Invalid frame length (%d)\n", len); + cfpkt_destroy(pkt); + return -EPROTO; + } len -= 2; + } if (cfpkt_setlen(pkt, len) < 0) { ++cffrml_rcv_error; -- 2.47.3