Begin forwarded message: Date: Fri, 15 Oct 2021 22:14:56 +0000 From: bugzilla-daemon@xxxxxxxxxxxxxxxxxxx To: stephen@xxxxxxxxxxxxxxxxxx Subject: [Bug 214729] New: Information leakage from kernel to user space in /net/bluetooth/hci_sock.c https://bugzilla.kernel.org/show_bug.cgi?id=214729 Bug ID: 214729 Summary: Information leakage from kernel to user space in /net/bluetooth/hci_sock.c Product: Networking Version: 2.5 Kernel Version: 5.15-rc5 Hardware: All OS: Linux Tree: Mainline Status: NEW Severity: high Priority: P1 Component: Other Assignee: stephen@xxxxxxxxxxxxxxxxxx Reporter: bao00065@xxxxxxx Regression: No Hi Maintainers, I recently reviewed the uninitialized value use bug in Linux kernel: https://syzkaller.appspot.com/bug?id=739ce0bc6e4097668cbf94c862f3b643b364d589. and patch: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b42b3a2744b3e8f427de79896720c72823af91ad The vulnerable function is: int __sys_getsockname(int fd, struct sockaddr __user *usockaddr, int __user *usockaddr_len) { struct socket *sock; struct sockaddr_storage address; // allocation int err, fput_needed; sock = sockfd_lookup_light(fd, &err, &fput_needed); if (!sock) goto out; err = security_socket_getsockname(sock); if (err) goto out_put; err = sock->ops->getname(sock, (struct sockaddr *)&address, 0); // initialization if (err < 0) goto out_put; /* "err" is actually length in this case */ err = move_addr_to_user(&address, err, usockaddr, usockaddr_len); //use out_put: fput_light(sock->file, fput_needed); out: return err; } static int move_addr_to_user(struct sockaddr_storage *kaddr, int klen, void __user *uaddr, int __user *ulen) { int err; int len; BUG_ON(klen > sizeof(struct sockaddr_storage)); err = get_user(len, ulen); if (err) return err; if (len > klen) len = klen; if (len < 0) return -EINVAL; if (len) { if (audit_sockaddr(klen, kaddr)) return -ENOMEM; if (copy_to_user(uaddr, kaddr, len)) // use return -EFAULT; } /* * "fromlen shall refer to the value before truncation.." * 1003.1g */ return __put_user(klen, ulen); } the variable address is allocated in __sys_getsockname, and then is initialized in sock->ops->getname(sock, (struct sockaddr *)& address, 0); After that, address is passed to move_addr_to_user() and finally it passed to copy_to_user(), leading to uninitialized value use. Main reason for this bug: initialization in sock->ops->getname(sock, (struct sockaddr *)&address, 0) is partially initialized. It only initializes the fields in the struct but not the holes between the fields. As a result, since uaddr will be passed to copy_to_user(), and the holes inside the uaddr struct contain uninitialized data inherited from the kernel stack, it may cause information leakage from kernel space to user space Here is the initialization function: static int isotp_getname(struct socket *sock, struct sockaddr *uaddr, int peer) { struct sockaddr_can *addr = (struct sockaddr_can *)uaddr; struct sock *sk = sock->sk; struct isotp_sock *so = isotp_sk(sk); if (peer) return -EOPNOTSUPP; +memset(addr, 0, ISOTP_MIN_NAMELEN);//patch addr->can_family = AF_CAN; addr->can_ifindex = so->ifindex; addr->can_addr.tp.rx_id = so->rxid; addr->can_addr.tp.tx_id = so->txid; return ISOTP_MIN_NAMELEN; } The patch: memset() initializes the whole struct sockaddr_can, including the holes within the struct sockaddr_can. Sockaddr_can is declared here: struct sockaddr_can { __kernel_sa_family_t can_family; int can_ifindex; union { /* transport protocol class address information (e.g. ISOTP) */ struct { canid_t rx_id, tx_id; } tp; /* J1939 address information */ struct { /* 8 byte name when using dynamic addressing */ __u64 name; /* pgn: * 8 bit: PS in PDU2 case, else 0 * 8 bit: PF * 1 bit: DP * 1 bit: reserved */ __u32 pgn; /* 1 byte address */ __u8 addr; } j1939; /* reserved for future CAN protocols address information */ } can_addr; }; There are a few holes inside the struct, but it doesn’t explicitly set to 0 in isotp_getname() At the same time, I realized sock->ops->getname(sock, (struct sockaddr *)&address, 0) is an indirect call. Thus it may go to different functions at the run time. If one of these functions doesn't initialize the holes within the struct, it may cause an information leak from kernel space to userspace. My tools find similar cloned bugs The same bug happen in /net/bluetooth/hci_sock.c s static int hci_sock_getname(struct socket *sock, struct sockaddr *addr, int peer) { struct sockaddr_hci *haddr = (struct sockaddr_hci *)addr; struct sock *sk = sock->sk; struct hci_dev *hdev; int err = 0; BT_DBG("sock %p sk %p", sock, sk); if (peer) return -EOPNOTSUPP; lock_sock(sk); hdev = hci_hdev_from_sock(sk); if (IS_ERR(hdev)) { err = PTR_ERR(hdev); goto done; } haddr->hci_family = AF_BLUETOOTH; haddr->hci_dev = hdev->id; haddr->hci_channel= hci_pi(sk)->channel; err = sizeof(*haddr); done: release_sock(sk); return err; } sockaddr_hci is declared here: struct sockaddr_hci { sa_family_t hci_family; unsigned short hci_dev; unsigned short hci_channel; }; We can see there is a hole between family and dev. Thus, we have to explicitly set the hole to zero. Otherwise, the address will be passed to copy_to_user and cause information leakage. Suggested patch: memset(maddr, 0, sizeof(sockaddr_hci)); Thank you for the review. I appreciate your time. Andrew Bao -- You may reply to this email to add a comment. You are receiving this mail because: You are the assignee for the bug.
