diff options
| author | Jann Horn <jannh@google.com> | 2025-02-12 21:15:15 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-02-14 11:21:56 +0300 |
| commit | e563b01208f4d1f609bcab13333b6c0e24ce6a01 (patch) | |
| tree | 6f4b453316081ee4221fb3b06d8f7e4875f408aa /drivers/usb/class/cdc-acm.c | |
| parent | c81d9fcd5b9402166048f377d4e5e0ee6f9ef26d (diff) | |
| download | linux-e563b01208f4d1f609bcab13333b6c0e24ce6a01.tar.xz | |
usb: cdc-acm: Check control transfer buffer size before access
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 ea2583529cd1
("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: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/class/cdc-acm.c')
| -rw-r--r-- | drivers/usb/class/cdc-acm.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 6b37d1c47fce..39c7db7bcd21 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -371,7 +371,7 @@ static void acm_process_notification(struct acm *acm, unsigned char *buf) static void acm_ctrl_irq(struct urb *urb) { struct acm *acm = urb->context; - struct usb_cdc_notification *dr = urb->transfer_buffer; + struct usb_cdc_notification *dr; unsigned int current_size = urb->actual_length; unsigned int expected_size, copy_size, alloc_size; int retval; @@ -398,9 +398,20 @@ static void acm_ctrl_irq(struct urb *urb) usb_mark_last_busy(acm->dev); - if (acm->nb_index) + if (acm->nb_index == 0) { + /* + * The first chunk of a message must contain at least the + * notification header with the length field, otherwise we + * can't get an expected_size. + */ + if (current_size < sizeof(struct usb_cdc_notification)) { + dev_dbg(&acm->control->dev, "urb too short\n"); + goto exit; + } + dr = urb->transfer_buffer; + } else { dr = (struct usb_cdc_notification *)acm->notification_buffer; - + } /* size = notification-header + (optional) data */ expected_size = sizeof(struct usb_cdc_notification) + le16_to_cpu(dr->wLength); |