CVE-2026-98551 — perf/core: Fill branch entries with a single assignment

Affected: Linux

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

perf/core: Fill branch entries with a single assignment

perf_clear_branch_entry_bitfields() clears the bitfields of struct perf_branch_entry one by one and leaves from/to alone, since callers overwrite those straight away. The list has to be kept in sync with the struct by hand and has already fallen behind: new_type and priv were added to perf_branch_entry and never added here.

Only BRBE writes those two, and neither for every record. brbe_set_perf_entry_type() leaves new_type alone for a branch type it does not recognise, and priv is not set for source-only records. arm_pmuv3.c allocates the per-CPU branch stack with kmalloc(), so such a record reaches userspace with whatever the slot held: uninitialised kmalloc() data on the first pass over the buffer, the previous record's values after that. Nothing under arch/x86/events/ writes either field, so only arm64 is affected.

Assign the whole entry at each site instead. Everything not named is then zero, and there is no list to keep in sync. The bitfields add up to exactly 64 bits, so the struct has no padding to leave undefined.

perf_clear_branch_entry_bitfields() has no callers left, so remove it. perf_entry_from_brbe_regset() assigns an empty literal instead, since it fills from/to conditionally. PERF_BR_SPEC_NA is 0, so dropping the explicit spec assignment changes nothing.

USN-8959-1 — linux, linux-aws, linux-gcp, linux-hwe-7.0, linux-ibm, linux-oracle vulnerabilities

Affected: Ubuntu:24.04:LTS: linux-hwe-7.0, Ubuntu:26.04:LTS: linux, Ubuntu:26.04:LTS: linux-aws, Ubuntu:26.04:LTS: linux-gcp, Ubuntu:26.04:LTS: linux-ibm, Ubuntu:26.04:LTS: linux-oracle

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: - USB Gadget drivers; - Memory management; - Multiple devices driver; - ARM64 architecture; - EROFS file system; - Networking core; - eXpress Data Path; - ARM32 architecture; - M68K architecture; - MIPS architecture; - OpenRISC architecture; - PA-RISC architecture; - PowerPC architecture; - RISC-V architecture; - S390 architecture; - User-Mode Linux (UML); - x86 architecture; - Block layer subsystem; - Cryptographic API; - Compute Acceleration Framework; - Intel NPU Driver; - Speakup Console Speech Driver; - ACPI drivers; - Serial ATA and Parallel ATA drivers; - Auxiliary display drivers; - Drivers core; - Micron PCIe SSD driver; - Null block device driver; - Ublk userspace block driver; - Compressed RAM block device driver; - Bluetooth drivers; - Bus devices; - AMD CDX bus driver; - Hardware random number generator core; - Character device driver; - TPM device driver; - Clock framework and drivers; - Clocksource drivers; - CPU frequency scaling framework; - CPU idle management framework; - Hardware crypto device drivers; - CXL (Compute Express Link) drivers; - DAX dirext access to differentiated memory framework; - DIBS (Direct Internal Buffer Sharing) drivers; - Buffer Sharing and Synchronization framework;…

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CVE-2026-98551 — perf/core: Fill branch entries with a single assignment

USN-8959-1 — linux, linux-aws, linux-gcp, linux-hwe-7.0, linux-ibm, linux-oracle vulnerabilities