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caif: fix integer underflow in cffrml_receive()

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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 <danisjiang@gmail.com>
Reported-by: Junrui Luo <moonafterrain@outlook.com>
Fixes: b482cd2053 ("net-caif: add CAIF core protocol stack")
Signed-off-by: Junrui Luo <moonafterrain@outlook.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/SYBPR01MB7881511122BAFEA8212A1608AFA6A@SYBPR01MB7881.ausprd01.prod.outlook.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Junrui Luo
2025-12-04 21:30:47 +08:00
committed by Jakub Kicinski
parent 71cfa7c893
commit 8a11ff0948
1 changed files with 8 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
net/caif/cffrml.c
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@@ -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;