CVE-2026-90347arm64: ptrace: Keep 'orig_x0' in-sync with x0 on syscall entry

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/a9e7743b1067ea38c4ad2665d40c3c4a920ad9a9
• https://git.kernel.org/stable/c/332c9c1a148d0425326989c1187face8f6b2a60c
• https://git.kernel.org/stable/c/ce17c651a90e242ad48df0df89b1e4cebcda5e14
• https://git.kernel.org/stable/c/e9e2854fcff5733ffc607e8ecc87e0e591ab41fd
• https://git.kernel.org/stable/c/f433869f23841a50455c4087d85540d5b4d37cde
• https://git.kernel.org/stable/c/88b839ce497ccb1ff92f7ae742c78dd2937ba572