CVE-2026-23383
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: bpf, arm64: Force 8-byte alignment for JIT buffer to prevent atomic tearing struct bpf_plt contains a u64 target field. Currently, the BPF JIT allocator requests an alignment of 4 bytes (sizeof(u32)) for the JIT buffer. Because the base address of the JIT buffer can be 4-byte aligned (e.g., ending in 0x4 or 0xc), the relative padding logic in build_plt() fails to ensure that target lands on an 8-byte boundary. This leads to two issues: 1. UBSAN reports misaligned-access warnings when dereferencing the structure. 2. More critically, target is updated concurrently via WRITE_ONCE() in bpf_arch_text_poke() while the JIT'd code executes ldr. On arm64, 64-bit loads/stores are only guaranteed to be single-copy atomic if they are 64-bit aligned. A misaligned target risks a torn read, causing the JIT to jump to a corrupted address. Fix this by increasing the allocation alignment requirement to 8 bytes (sizeof(u64)) in bpf_jit_binary_pack_alloc(). This anchors the base of the JIT buffer to an 8-byte boundary, allowing the relative padding math in build_plt() to correctly align the target field.
Severity
HIGH
CVSS score
7.8
(v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-03-25 11:16:38.487000
Last modified
2026-10-30 13:18:37.760000
View original CVE JSON
{
"id": "CVE-2026-23383",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-03-25T11:16:38.487",
"lastModified": "2026-10-30T13:18:37.760",
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{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf, arm64: Force 8-byte alignment for JIT buffer to prevent atomic tearing\n\nstruct bpf_plt contains a u64 target field. Currently, the BPF JIT\nallocator requests an alignment of 4 bytes (sizeof(u32)) for the JIT\nbuffer.\n\nBecause the base address of the JIT buffer can be 4-byte aligned (e.g.,\nending in 0x4 or 0xc), the relative padding logic in build_plt() fails\nto ensure that target lands on an 8-byte boundary.\n\nThis leads to two issues:\n1. UBSAN reports misaligned-access warnings when dereferencing the\n structure.\n2. More critically, target is updated concurrently via WRITE_ONCE() in\n bpf_arch_text_poke() while the JIT'd code executes ldr. On arm64,\n 64-bit loads/stores are only guaranteed to be single-copy atomic if\n they are 64-bit aligned. A misaligned target risks a torn read,\n causing the JIT to jump to a corrupted address.\n\nFix this by increasing the allocation alignment requirement to 8 bytes\n(sizeof(u64)) in bpf_jit_binary_pack_alloc(). This anchors the base of\nthe JIT buffer to an 8-byte boundary, allowing the relative padding math\nin build_plt() to correctly align the target field."
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{
"lang": "es",
"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nbpf, arm64: Forzar alineación de 8 bytes para el búfer JIT para prevenir el desgarro atómico\n\nstruct bpf_plt contiene un campo objetivo u64. Actualmente, el asignador JIT de BPF solicita una alineación de 4 bytes (sizeof(u32)) para el búfer JIT.\n\nDebido a que la dirección base del búfer JIT puede estar alineada a 4 bytes (p. ej., terminando en 0x4 o 0xc), la lógica de relleno relativo en build_plt() no logra asegurar que target caiga en un límite de 8 bytes.\n\nEsto lleva a dos problemas:\n1. UBSAN informa advertencias de acceso desalineado al desreferenciar la estructura.\n2. Más críticamente, target se actualiza concurrentemente a través de WRITE_ONCE() en bpf_arch_text_poke() mientras el código JIT'd ejecuta ldr. En arm64, las cargas/almacenamientos de 64 bits solo se garantiza que sean atómicos de copia única si están alineados a 64 bits. Un target desalineado arriesga una lectura desgarrada, haciendo que el JIT salte a una dirección corrupta.\n\nSolucione esto aumentando el requisito de alineación de asignación a 8 bytes (sizeof(u64)) en bpf_jit_binary_pack_alloc(). Esto ancla la base del búfer JIT a un límite de 8 bytes, permitiendo que las matemáticas de relleno relativo en build_plt() alineen correctamente el campo target."
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