From: Jiale Yao Date: Wed, 22 Jul 2026 09:26:14 +0000 (+0800) Subject: Bluetooth: RFCOMM: validate skb length in rfcomm_recv_frame X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b230e5bf501c5edaf2eb0991cb862ac142031d4b;p=thirdparty%2Fkernel%2Fstable.git 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). Signed-off-by: Jiale Yao Signed-off-by: Luiz Augusto von Dentz --- diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c index 75f7512dec54..2e8c080b4d9e 100644 --- a/net/bluetooth/rfcomm/core.c +++ b/net/bluetooth/rfcomm/core.c @@ -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);