CVE-2024-50102 — x86: fix user address masking non-canonical speculation issue

Affected: Linux

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

x86: fix user address masking non-canonical speculation issue

It turns out that AMD has a "Meltdown Lite(tm)" issue with non-canonical accesses in kernel space. And so using just the high bit to decide whether an access is in user space or kernel space ends up with the good old "leak speculative data" if you have the right gadget using the result:

CVE-2020-12965 “Transient Execution of Non-Canonical Accesses“

Now, the kernel surrounds the access with a STAC/CLAC pair, and those instructions end up serializing execution on older Zen architectures, which closes the speculation window.

But that was true only up until Zen 5, which renames the AC bit [1]. That improves performance of STAC/CLAC a lot, but also means that the speculation window is now open.

Note that this affects not just the new address masking, but also the regular valid_user_address() check used by access_ok(), and the asm version of the sign bit check in the get_user() helpers.

It does not affect put_user() or clear_user() variants, since there's no speculative result to be used in a gadget for those operations.

USN-7276-1 — linux, linux-lowlatency vulnerabilities

Affected: Ubuntu:24.10: linux, Ubuntu:24.10: linux-lowlatency

Attila Szász discovered that the HFS+ file system implementation in the Linux Kernel contained a heap overflow vulnerability. An attacker could use a specially crafted file system image that, when mounted, could cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2025-0927)

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: - ARM32 architecture; - ARM64 architecture; - PowerPC architecture; - RISC-V architecture; - S390 architecture; - SuperH RISC architecture; - User-Mode Linux (UML); - x86 architecture; - Block layer subsystem; - Cryptographic API; - Compute Acceleration Framework; - ACPI drivers; - Drivers core; - ATA over ethernet (AOE) driver; - RAM backed block device driver; - Network block device driver; - Ublk userspace block driver; - Compressed RAM block device driver; - Bluetooth drivers; - TPM device driver; - Clock framework and drivers; - Data acquisition framework and drivers; - CPU frequency scaling framework; - Hardware crypto device drivers; - CXL (Compute Express Link) drivers; - DAX dirext access to differentiated memory framework; - Buffer Sharing and Synchronization framework; - EDAC drivers; - FireWire subsystem; - ARM SCMI message protocol; - ARM SCPI message protocol; - EFI core; - Qualcomm firmware drivers; - GPIO subsystem;…

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CVE-2024-50102 — x86: fix user address masking non-canonical speculation issue

USN-7276-1 — linux, linux-lowlatency vulnerabilities