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).
