5.4-stable review patch. If anyone has any objections, please let me know.
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From: Jann Horn jannh@google.com
commit 12e712964f41d05ae034989892de445781c46730 upstream.
If we receive an initial fragment of size 8 bytes which specifies a wLength of 1 byte (so the reassembled message is supposed to be 9 bytes long), and we then receive a second fragment of size 9 bytes (which is not supposed to happen), we currently wrongly bypass the fragment reassembly code but still pass the pointer to the acm->notification_buffer to acm_process_notification().
Make this less wrong by always going through fragment reassembly when we expect more fragments.
Before this patch, receiving an overlong fragment could lead to `newctrl` in acm_process_notification() being uninitialized data (instead of data coming from the device).
Cc: stable stable@kernel.org Fixes: ea2583529cd1 ("cdc-acm: reassemble fragmented notifications") Signed-off-by: Jann Horn jannh@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/class/cdc-acm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -404,7 +404,7 @@ static void acm_ctrl_irq(struct urb *urb expected_size = sizeof(struct usb_cdc_notification) + le16_to_cpu(dr->wLength);
- if (current_size < expected_size) { + if (acm->nb_index != 0 || current_size < expected_size) { /* notification is transmitted fragmented, reassemble */ if (acm->nb_size < expected_size) { u8 *new_buffer;