From: Soenke Huster <soenke.huster@eknoes.de>
To: Marcel Holtmann <marcel@holtmann.org>,
Johan Hedberg <johan.hedberg@gmail.com>,
Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>
Cc: Soenke Huster <soenke.huster@eknoes.de>,
linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH v2] Bluetooth: RFCOMM: Use skb_trim to trim checksum
Date: Fri, 10 Jun 2022 13:07:49 +0200 [thread overview]
Message-ID: <20220610110749.110881-1-soenke.huster@eknoes.de> (raw)
As skb->tail might be zero, it can underflow. This leads to a page
fault: skb_tail_pointer simply adds skb->tail (which is now MAX_UINT)
to skb->head.
BUG: unable to handle page fault for address: ffffed1021de29ff
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
RIP: 0010:rfcomm_run+0x831/0x4040 (net/bluetooth/rfcomm/core.c:1751)
By using skb_trim instead of the direct manipulation, skb->tail
is reset. Thus, the correct pointer to the checksum is used.
Signed-off-by: Soenke Huster <soenke.huster@eknoes.de>
---
v2: Clarified how the bug triggers, minimize code change
net/bluetooth/rfcomm/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
index 7324764384b6..443b55edb3ab 100644
--- a/net/bluetooth/rfcomm/core.c
+++ b/net/bluetooth/rfcomm/core.c
@@ -1747,7 +1747,7 @@ static struct rfcomm_session *rfcomm_recv_frame(struct rfcomm_session *s,
type = __get_type(hdr->ctrl);
/* Trim FCS */
- skb->len--; skb->tail--;
+ skb_trim(skb, skb->len - 1);
fcs = *(u8 *)skb_tail_pointer(skb);
if (__check_fcs(skb->data, type, fcs)) {
--
2.36.1
next reply other threads:[~2022-06-10 11:08 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-10 11:07 Soenke Huster [this message]
2022-06-10 11:57 ` [v2] Bluetooth: RFCOMM: Use skb_trim to trim checksum bluez.test.bot
2022-06-10 13:59 ` [PATCH v2] " Eric Dumazet
2022-06-10 15:35 ` Sönke Huster
2022-06-10 16:55 ` Eric Dumazet
2022-06-14 13:42 ` Sönke Huster
2022-06-14 14:17 ` Eric Dumazet
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