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commit e563b01208f4d1f609bcab13333b6c0e24ce6a01 upstream. If the first fragment is shorter than struct usb_cdc_notification, we can't calculate an expected_size. Log an error and discard the notification instead of reading lengths from memory outside the received data, which can lead to memory corruption when the expected_size decreases between fragments, causing `expected_size - acm->nb_index` to wrap. This issue has been present since the beginning of git history; however, it only leads to memory corruption since commit ea258352 ("cdc-acm: reassemble fragmented notifications"). A mitigating factor is that acm_ctrl_irq() can only execute after userspace has opened /dev/ttyACM*; but if ModemManager is running, ModemManager will do that automatically depending on the USB device's vendor/product IDs and its other interfaces. Cc: stable <stable@kernel.org> Fixes: 1da177e4 ("Linux-2.6.12-rc2") Signed-off-by:
Jann Horn <jannh@google.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit e563b01208f4d1f609bcab13333b6c0e24ce6a01 upstream. If the first fragment is shorter than struct usb_cdc_notification, we can't calculate an expected_size. Log an error and discard the notification instead of reading lengths from memory outside the received data, which can lead to memory corruption when the expected_size decreases between fragments, causing `expected_size - acm->nb_index` to wrap. This issue has been present since the beginning of git history; however, it only leads to memory corruption since commit ea258352 ("cdc-acm: reassemble fragmented notifications"). A mitigating factor is that acm_ctrl_irq() can only execute after userspace has opened /dev/ttyACM*; but if ModemManager is running, ModemManager will do that automatically depending on the USB device's vendor/product IDs and its other interfaces. Cc: stable <stable@kernel.org> Fixes: 1da177e4 ("Linux-2.6.12-rc2") Signed-off-by:
