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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , Shuah Khan , netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, AutonomousCodeSecurity@microsoft.com, Xiang Mei , tgopinath@linux.microsoft.com, kys@microsoft.com, Cen Zhang Subject: [PATCH net v4 0/2] amt: send the relay's General Query directly from the receive path Date: Mon, 28 Sep 2026 23:23:10 +0300 Message-ID: <20260928202312.74574-1-omar@blockcast.net> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The relay queues its General Query on the amt device with a raw tunnel pointer in skb->cb, and a query that waits in a qdisc can outlive its tunnel: a use-after-free in amt_dev_xmit(), reported by Microsoft with a KASAN reproducer. Patch 1 sends the query directly from amt_request_handler(), inside the RCU section that found or created the tunnel, so it never waits in a qdisc and nothing is stored in skb->cb. Patch 2 adds the selftest Taehee asked for. It counts the queries that leave the relay through its amt device and expects none. It fails without patch 1 and passes with it. v4: patch 1 is unchanged from v3; patch 2 is new. v3: https://lore.kernel.org/netdev/20260928181601.85857-1-omar@blockcast.net/ v2: https://lore.kernel.org/netdev/20260922214150.13970-1-cenzhang@linux.microsoft.com/ Omar Ramadan (2): amt: send the relay's General Query directly from the receive path selftests: net: amt: check that the relay's queries bypass the amt device drivers/net/amt.c | 48 ++++++++++-------------------- include/net/amt.h | 4 --- tools/testing/selftests/net/amt.sh | 29 ++++++++++++++++++ 3 files changed, 44 insertions(+), 37 deletions(-) base-commit: a7bfaba4823e3c165bb2004c74eff7c096672bc7 -- 2.47.3