arm64: ptrace: Keep 'orig_x0' in-sync with x0 on syscall entry

Summary

In the Linux kernel, the following vulnerability has been resolved: arm64: ptrace: Keep 'orig_x0' in-sync with x0 on syscall entry Commit e057b9477232 ("arm64: syscall: Ensure saved x0 is kept in-sync with tracer updates") attempted to resolve a long-standing issue with syscall entry tracing, where a tracer is able to manipulate the first syscall argument without being subjected to seccomp or audit checking. Unfortunately, that fix was incomplete [1], as it failed to update 'orig_x0' between a tracer updating x0 during a seccomp ptrace exit (SECCOMP_RET_TRACE) and the seccomp filter being re-evaluated. Rather than add hooks to the core seccomp code, instead move the synchronisation code into the ptrace GPR and syscall setting code so that 'orig_x0' is kept up to date with x0 whenever we're stopped on the syscall entry path.

Timeline

1. Sep 17, 2026, 4:08 PM UTCCVE published
2. Oct 21, 2026, 12:51 PM UTCRecord last updated

Affected versions

• Linux Linux

  From a5cd110cb8369d6b37ef5ccfe56b3fa1338c9615 · fixed in 332c9c1a148d0425326989c1187face8f6b2a60c; From a5cd110cb8369d6b37ef5ccfe56b3fa1338c9615 · fixed in ce17c651a90e242ad48df0df89b1e4cebcda5e14; From a5cd110cb8369d6b37ef5ccfe56b3fa1338c9615 · fixed in e9e2854fcff5733ffc607e8ecc87e0e591ab41fd; From a5cd110cb8369d6b37ef5ccfe56b3fa1338c9615 · fixed in f433869f23841a50455c4087d85540d5b4d37cde; From a5cd110cb8369d6b37ef5ccfe56b3fa1338c9615 · fixed in 88b839ce497ccb1ff92f7ae742c78dd2937ba572

• Linux Linux

  4.8

• KernelLinux

  From 4.8.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.114; From 6.13.0 · fixed in 6.18.57; From 6.19.0 · fixed in 7.2.6

References 5