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From: Kees Cook <keescook@chromium.org>
To: Marcel Holtmann <marcel@holtmann.org>
Cc: Kees Cook <keescook@chromium.org>,
	Johan Hedberg <johan.hedberg@gmail.com>,
	Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: [PATCH] Bluetooth: mgmt: Pessimize compile-time bounds-check
Date: Tue, 17 Aug 2021 21:39:12 -0700	[thread overview]
Message-ID: <20210818043912.1466447-1-keescook@chromium.org> (raw)

After gaining __alloc_size hints, GCC thinks it can reach a memcpy()
with eir_len == 0 (since it can't see into the rewrite of status).
Instead, check eir_len == 0, avoiding this future warning:

In function 'eir_append_data',
    inlined from 'read_local_oob_ext_data_complete' at net/bluetooth/mgmt.c:7210:12:
./include/linux/fortify-string.h:54:29: warning: '__builtin_memcpy' offset 5 is out of the bounds [0, 3] [-Warray-bounds]
...
net/bluetooth/hci_request.h:133:2: note: in expansion of macro 'memcpy'
  133 |  memcpy(&eir[eir_len], data, data_len);
      |  ^~~~~~

Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: linux-bluetooth@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 net/bluetooth/mgmt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
index 1e21e014efd2..cea01e275f1e 100644
--- a/net/bluetooth/mgmt.c
+++ b/net/bluetooth/mgmt.c
@@ -7204,7 +7204,7 @@ static void read_local_oob_ext_data_complete(struct hci_dev *hdev, u8 status,
 	if (!mgmt_rp)
 		goto done;
 
-	if (status)
+	if (eir_len == 0)
 		goto send_rsp;
 
 	eir_len = eir_append_data(mgmt_rp->eir, 0, EIR_CLASS_OF_DEV,
-- 
2.30.2


             reply	other threads:[~2021-08-18  4:39 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18  4:39 Kees Cook [this message]
2021-08-19 14:52 ` Marcel Holtmann

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