Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

arm64: asm-bug: Add .align 2 to the end of __BUG_ENTRY

When CONFIG_DEBUG_BUGVERBOSE=n, we fail to add necessary padding bytes to bug_table entries, and as a result the last entry in a bug table will be ignored, potentially leading to an unexpected panic(). All prior entries in the table will be handled correctly.

The arm64 ABI requires that struct fields of up to 8 bytes are naturally-aligned, with padding added within a struct such that struct are suitably aligned within arrays.

When CONFIG_DEBUG_BUGVERPOSE=y, the layout of a bug_entry is:

struct bug_entry { signed int bug_addr_disp; // 4 bytes signed int file_disp; // 4 bytes unsigned short line; // 2 bytes unsigned short flags; // 2 bytes }

... with 12 bytes total, requiring 4-byte alignment.

When CONFIG_DEBUG_BUGVERBOSE=n, the layout of a bug_entry is:

struct bug_entry { signed int bug_addr_disp; // 4 bytes unsigned short flags; // 2 bytes < implicit padding > // 2 bytes }

... with 8 bytes total, with 6 bytes of data and 2 bytes of trailing padding, requiring 4-byte alginment.

When we create a bug_entry in assembly, we align the start of the entry to 4 bytes, which implicitly handles padding for any prior entries. However, we do not align the end of the entry, and so when CONFIG_DEBUG_BUGVERBOSE=n, the final entry lacks the trailing padding bytes.

For the main kernel image this is not a problem as find_b…

Affected: Ubuntu:Pro:18.04:LTS: linux-aws-5.4, Ubuntu:Pro:18.04:LTS: linux-gcp-5.4, Ubuntu:Pro:18.04:LTS: linux-hwe-5.4, Ubuntu:Pro:18.04:LTS: linux-ibm-5.4, Ubuntu:20.04:LTS: linux, Ubuntu:20.04:LTS: linux-aws, Ubuntu:20.04:LTS: linux-gcp, Ubuntu:20.04:LTS: linux-gkeop, Ubuntu:20.04:LTS: linux-ibm, Ubuntu:20.04:LTS: linux-iot and 3 more

Several security issues were discovered in the Linux kernel. An attacker could possibly use these to compromise the system. This update corrects flaws in the following subsystems: - ARM64 architecture; - M68K architecture; - User-Mode Linux (UML); - x86 architecture; - Accessibility subsystem; - Character device driver; - Clock framework and drivers; - CPU frequency scaling framework; - Hardware crypto device drivers; - Buffer Sharing and Synchronization framework; - FireWire subsystem; - GPU drivers; - HW tracing; - Macintosh device drivers; - Multiple devices driver; - Media drivers; - Network drivers; - Pin controllers subsystem; - S/390 drivers; - SCSI drivers; - SoundWire subsystem; - Greybus lights staging drivers; - TTY drivers; - Framebuffer layer; - Virtio drivers; - 9P distributed file system; - eCrypt file system; - EROFS file system; - Ext4 file system; - F2FS file system; - JFFS2 file system; - Network file system client; - NILFS2 file system; - SMB network file system; - Kernel debugger infrastructure; - IRQ subsystem; - Tracing infrastructure; - Dynamic debug library; - 9P file system network protocol; - Bluetooth subsystem; - Networking core; - IPv4 networking; - IPv6 networking; - Netfilter; - NET/ROM layer; - NFC subsystem; - NSH protocol; - Open vSwitch; - Phonet protocol; - TIPC protocol; - Unix domain sockets; - Wireless networking; - eXpress Data Pa…