CVE-2017-1000112

Linux kernel: Existe una corrupción de memoria explotable debida al cambio de ruta de UFO a no UFO. Al crear un paquete UFO con MSG_MORE, __ip_append_data() llama a ip_ufo_append_data() para que se anexe. Sin embargo, entre dos llamadas send(), la ruta anexa puede cambiarse de UFO a no UFO, lo que lleva a una corrupción de memoria. Si la longitud del paquete UFO sobrepasa el MTU, copy = maxfraglen - skb->len se convierte en negativo en la ruta no UFO y se toma una rama para asignar un nuevo skb. Esto desencadena la fragmentación y el cálculo de fraggap = skb_prev->len - maxfraglen. fraggap puede exceder el MTU, lo que provoca que copy = datalen - transhdrlen - fraggap se vuelva negativo. En consecuencia, skb_copy_and_csum_bits() escribe fuera de límites. Existe un problema similar en el código IPv6. Este error fue introducido en e89e9cf539a2 ("[IPv4/IPv6]: UFO Scatter-gather approach") el 18 de octubre de 2005.

An exploitable memory corruption flaw was found in the Linux kernel. The append path can be erroneously switched from UFO to non-UFO in ip_ufo_append_data() when building an UFO packet with MSG_MORE option. If unprivileged user namespaces are available, this flaw can be exploited to gain root privileges.

An update that solves four vulnerabilities and has one errata is now available. This update for the Linux Kernel 3.12.74-60_64_60 fixes several issues. The following security bugs were fixed. Security/keys/keyctl.c in the Linux kernel did not consider the case of a NULL payload in conjunction with a nonzero length value, which allowed local users to cause a denial of service (NULL pointer dereference and OOPS) via a crafted add_key or keyctl system call. Updated patch for this issue to be in sync with the other livepatches. Description of the issue: Prevent race condition in net-packet code that could have been exploited by unprivileged users to gain root access. The __ip6_append_data function in net/ipv6/ip6_output.c was too late in checking whether an overwrite of an skb data structure may occur, which allowed local users to cause a denial of service via crafted system calls. The inet_csk_clone_lock function in net/ipv4/inet_connection_sock.c allowed attackers to cause a denial of service or possibly have unspecified other impact by leveraging use of the accept system call.