Linux Kernel bpf JIT ARM64 Misaligned Target Causing Atomic Tearing
CVE-2026-23383 Published on March 25, 2026
bpf, arm64: Force 8-byte alignment for JIT buffer to prevent atomic tearing
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.
Products Associated with CVE-2026-23383
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Affected Versions
Linux:- Version b2ad54e1533e91449cb2a371e034942bd7882b58 and below 80ad264da02cc4aee718e799c2b79f0f834673dc is affected.
- Version b2ad54e1533e91449cb2a371e034942bd7882b58 and below 519b1ad91de5bf7a496f2b858e9212db6328e1de is affected.
- Version b2ad54e1533e91449cb2a371e034942bd7882b58 and below 66959ed481a474eaae278c7f6860a2a9b188a4d6 is affected.
- Version b2ad54e1533e91449cb2a371e034942bd7882b58 and below ef06fd16d48704eac868441d98d4ef083d8f3d07 is affected.
- Version 6.0 is affected.
- Before 6.0 is unaffected.
- Version 6.12.77, <= 6.12.* is unaffected.
- Version 6.18.17, <= 6.18.* is unaffected.
- Version 6.19.7, <= 6.19.* is unaffected.
- Version 7.0-rc2, <= * is unaffected.