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[24.12.10.127]) by smtp.gmail.com with ESMTPSA id 00721157ae682-798dee4a70bsm28803647b3.32.2026.03.07.22.21.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 07 Mar 2026 22:21:51 -0800 (PST) From: Tyllis Xu X-Google-Original-From: Tyllis Xu To: gregkh@linuxfoundation.org Cc: arnd@arndb.de, linux-kernel@vger.kernel.org, stable@vger.kernel.org, ychen@northwestern.edu, danisjiang@gmail.com, Tyllis Xu Subject: [PATCH] misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt() Date: Sun, 8 Mar 2026 00:21:08 -0600 Message-ID: <20260308062108.258940-1-LivelyCarpet87@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" ibmasm_handle_mouse_interrupt() performs an out-of-bounds MMIO read when the queue reader or writer index from hardware exceeds REMOTE_QUEUE_SIZE (60). A compromised service processor can trigger this by writing an out-of-range value to the reader or writer MMIO register before asserting an interrupt. Since writer is re-read from hardware on every loop iteration, it can also be set to an out-of-range value after the loop has already started. The root cause is that get_queue_reader() and get_queue_writer() return raw readl() values that are passed directly into get_queue_entry(), which computes: queue_begin + reader * sizeof(struct remote_input) with no bounds check. This unchecked MMIO address is then passed to memcpy_fromio(), reading 8 bytes from unintended device registers. For sufficiently large values the address falls outside the PCI BAR mapping entirely, triggering a machine check exception. Fix by checking both indices against REMOTE_QUEUE_SIZE at the top of the loop body, before any call to get_queue_entry(). On an out-of-range value, reset the reader register to 0 via set_queue_reader() before breaking, so that normal queue operation can resume if the corrupted hardware state is transient. Reported-by: Yuhao Jiang Fixes: 278d72ae8803 ("[PATCH] ibmasm driver: redesign handling of remote co= ntrol events") Cc: stable@vger.kernel.org Cc: ychen@northwestern.edu Signed-off-by: Tyllis Xu --- drivers/misc/ibmasm/remote.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/misc/ibmasm/remote.c b/drivers/misc/ibmasm/remote.c index ec816d3b38cb..521531738c9a 100644 --- a/drivers/misc/ibmasm/remote.c +++ b/drivers/misc/ibmasm/remote.c @@ -177,6 +177,11 @@ void ibmasm_handle_mouse_interrupt(struct service_proc= essor *sp) writer =3D get_queue_writer(sp); =20 while (reader !=3D writer) { + if (reader >=3D REMOTE_QUEUE_SIZE || writer >=3D REMOTE_QUEUE_SIZE) { + set_queue_reader(sp, 0); + break; + } + memcpy_fromio(&input, get_queue_entry(sp, reader), sizeof(struct remote_input)); =20 --=20 2.43.0