Linux Kernel

In the Linux kernel through 5.2.1 on the powerpc platform, when hardware transactional memory is disabled, a local user can cause a denial of service (TM Bad Thing exception and system crash) via a sigreturn() system call that sends a crafted signal frame. This affects arch/powerpc/kernel/signal_32.c and arch/powerpc/kernel/signal_64.c.Show less

In the Linux kernel before 5.1.17, ptrace_link in kernel/ptrace.c mishandles the recording of the credentials of a process that wants to create a ptrace relationship, which allows local users to obtain root access by leveraging certain scenarios with a parent-child process relationship, where a parent drops privileges and calls execve (potentially allowing control by an attacker). One contributing factor is an object lifetime issue (which can also cause a panic). Another contributing factor is incorrect marking of a ptrace relationship as privileged, which is exploitable through (for example) Polkit's pkexec helper with PTRACE_TRACEME. NOTE: SELinux deny_ptrace might be a usable workaround in some environments.Show less

The Linux kernel 4.x (starting from 4.1) and 5.x before 5.0.8 allows Information Exposure (partial kernel address disclosure), leading to a KASLR bypass. Specifically, it is possible to extract the KASLR kernel image offset using the IP ID values the kernel produces for connection-less protocols (e.g., UDP and ICMP). When such traffic is sent to multiple destination IP addresses, it is possible to obtain hash collisions (of indices to the counter array) and thereby obtain the hashing key (via enumeration). This key contains enough bits from a kernel address (of a static variable) so when the key is extracted (via enumeration), the offset of the kernel image is exposed. This attack can be carried out remotely, by the attacker forcing the target device to send UDP or ICMP (or certain other) traffic to attacker-controlled IP addresses. Forcing a server to send UDP traffic is trivial if the server is a DNS server. ICMP traffic is trivial if the server answers ICMP Echo requests (ping). For client targets, if the target visits the attacker's web page, then WebRTC or gQUIC can be used to force UDP traffic to attacker-controlled IP addresses. NOTE: this attack against KASLR became viable in 4.1 because IP ID generation was changed to have a dependency on an address associated with a network namespace.Show less

In the Linux kernel before 5.1.7, a device can be tracked by an attacker using the IP ID values the kernel produces for connection-less protocols (e.g., UDP and ICMP). When such traffic is sent to multiple destination IP addresses, it is possible to obtain hash collisions (of indices to the counter array) and thereby obtain the hashing key (via enumeration). An attack may be conducted by hosting a crafted web page that uses WebRTC or gQUIC to force UDP traffic to attacker-controlled IP addresses.Show less

A NULL pointer dereference vulnerability in the function nfc_genl_deactivate_target() in net/nfc/netlink.c in the Linux kernel before 5.1.13 can be triggered by a malicious user-mode program that omits certain NFC attributes, leading to denial of service.Show less

arch/powerpc/mm/mmu_context_book3s64.c in the Linux kernel before 5.1.15 for powerpc has a bug where unrelated processes may be able to read/write to one another's virtual memory under certain conditions via an mmap above 512 TB. Only a subset of powerpc systems are affected.Show less

Jonathan Looney discovered that the Linux kernel default MSS is hard-coded to 48 bytes. This allows a remote peer to fragment TCP resend queues significantly more than if a larger MSS were enforced. A remote attacker could use this to cause a denial of service. This has been fixed in stable kernel releases 4.4.182, 4.9.182, 4.14.127, 4.19.52, 5.1.11, and is fixed in commits 967c05aee439e6e5d7d805e195b3a20ef5c433d6 and 5f3e2bf008c2221478101ee72f5cb4654b9fc363.Show less

Jonathan Looney discovered that the TCP retransmission queue implementation in tcp_fragment in the Linux kernel could be fragmented when handling certain TCP Selective Acknowledgment (SACK) sequences. A remote attacker could use this to cause a denial of service. This has been fixed in stable kernel releases 4.4.182, 4.9.182, 4.14.127, 4.19.52, 5.1.11, and is fixed in commit f070ef2ac66716357066b683fb0baf55f8191a2e.Show less

Jonathan Looney discovered that the TCP_SKB_CB(skb)->tcp_gso_segs value was subject to an integer overflow in the Linux kernel when handling TCP Selective Acknowledgments (SACKs). A remote attacker could use this to cause a denial of service. This has been fixed in stable kernel releases 4.4.182, 4.9.182, 4.14.127, 4.19.52, 5.1.11, and is fixed in commit 3b4929f65b0d8249f19a50245cd88ed1a2f78cff.Show less

i915_gem_userptr_get_pages in drivers/gpu/drm/i915/i915_gem_userptr.c in the Linux kernel 4.15.0 on Ubuntu 18.04.2 allows local users to cause a denial of service (NULL pointer dereference and BUG) or possibly have unspecified other impact via crafted ioctl calls to /dev/dri/card0.Show less

An issue was discovered in the Linux kernel before 5.0. The function __mdiobus_register() in drivers/net/phy/mdio_bus.c calls put_device(), which will trigger a fixed_mdio_bus_init use-after-free. This will cause a denial of service.Show less

An issue was discovered in the Linux kernel before 4.20.15. The nfc_llcp_build_tlv function in net/nfc/llcp_commands.c may return NULL. If the caller does not check for this, it will trigger a NULL pointer dereference. This will cause denial of service. This affects nfc_llcp_build_gb in net/nfc/llcp_core.c.Show less

An issue was discovered in get_vdev_port_node_info in arch/sparc/kernel/mdesc.c in the Linux kernel through 5.1.6. There is an unchecked kstrdup_const of node_info->vdev_port.name, which might allow an attacker to cause a denial of service (NULL pointer dereference and system crash).Show less