In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: RFCOMM: validate skb length in rfcomm recv frame

rfcomm recv frame() casts skb->data to struct rfcomm hdr and dereferences hdr->addr and hdr->ctrl without validating skb->len first. A truncated frame with skb->len less than the minimum header size causes an out-of-bounds read of uninitialized memory. Additionally, a zero-length frame causes skb->len-- to underflow to UINT MAX, making skb tail pointer() read far past the buffer.

Commit 23882b828c3c ("Bluetooth: RFCOMM: validate skb length in MCC handlers") fixed the same class of missing-length-check bugs in the MCC sub-handlers, but the top-level rfcomm recv frame() was left unfixed. KMSAN reports:

BUG: KMSAN: uninit-value in rfcomm run ... Uninit was created at: alloc skb+0x474/0xb60 vhci write+0xe9/0x870

Fix this by rejecting frames smaller than sizeof(struct rfcomm hdr) + 1 (the minimum frame must have a 3-byte header and a 1-byte FCS).