In general, accessing userspace memory beyond the length of the supplied buffer in VFS read/write handlers can lead to both kernel memory corruption (via kernel_read()/kernel_write(), which can e.g. be triggered via sys_splice()) and privilege escalation inside userspace.
Fixes: 286468210d83 ("firewire: new driver: nosy - IEEE 1394 traffic sniffer") Signed-off-by: Jann Horn <ja...@google.com> --- No CC stable because this device shouldn't be available to unprivileged code by default and should be pretty rare. drivers/firewire/nosy.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/firewire/nosy.c b/drivers/firewire/nosy.c index a128dd1126ae..732075fc312e 100644 --- a/drivers/firewire/nosy.c +++ b/drivers/firewire/nosy.c @@ -161,11 +161,12 @@ packet_buffer_get(struct client *client, char __user *data, size_t user_length) if (atomic_read(&buffer->size) == 0) return -ENODEV; - /* FIXME: Check length <= user_length. */ - end = buffer->data + buffer->capacity; length = buffer->head->length; + if (length > user_length) + return -EINVAL; + if (&buffer->head->data[length] < end) { if (copy_to_user(data, buffer->head->data, length)) return -EFAULT; -- 2.18.0.399.gad0ab374a1-goog