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Bluetooth: RFCOMM: validate skb length in rfcomm_recv_frame

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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 23882b828c ("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).

Signed-off-by: Jiale Yao <yaojiale02@163.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
This commit is contained in:
Jiale Yao 2026-07-22 17:26:14 +08:00 committed by Luiz Augusto von Dentz
parent c4740e7f23
commit b230e5bf50
1 changed files with 5 additions and 0 deletions
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5
net/bluetooth/rfcomm/core.c
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@ -1795,6 +1795,11 @@ static struct rfcomm_session *rfcomm_recv_frame(struct rfcomm_session *s,
return s;
}
if (skb->len < sizeof(*hdr) + 1) {
kfree_skb(skb);
return s;
}
dlci = __get_dlci(hdr->addr);
type = __get_type(hdr->ctrl);