This is a note to let you know that I've just added the patch titled arm64: ptrace: Fix seccomp of traced syscall -1 (NO_SYSCALL) to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: arm64-ptrace-fix-seccomp-of-traced-syscall-1-no_syscall.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From df84fe94708985cdfb78a83148322bcd0a699472 Mon Sep 17 00:00:00 2001 From: Timothy E Baldwin <T.E.Baldwin99@xxxxxxxxxxxxxxxxxxx> Date: Sat, 16 Jan 2021 15:18:54 +0000 Subject: arm64: ptrace: Fix seccomp of traced syscall -1 (NO_SYSCALL) From: Timothy E Baldwin <T.E.Baldwin99@xxxxxxxxxxxxxxxxxxx> commit df84fe94708985cdfb78a83148322bcd0a699472 upstream. Since commit f086f67485c5 ("arm64: ptrace: add support for syscall emulation"), if system call number -1 is called and the process is being traced with PTRACE_SYSCALL, for example by strace, the seccomp check is skipped and -ENOSYS is returned unconditionally (unless altered by the tracer) rather than carrying out action specified in the seccomp filter. The consequence of this is that it is not possible to reliably strace a seccomp based implementation of a foreign system call interface in which r7/x8 is permitted to be -1 on entry to a system call. Also trace_sys_enter and audit_syscall_entry are skipped if a system call is skipped. Fix by removing the in_syscall(regs) check restoring the previous behaviour which is like AArch32, x86 (which uses generic code) and everything else. Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Catalin Marinas<catalin.marinas@xxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Fixes: f086f67485c5 ("arm64: ptrace: add support for syscall emulation") Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Reviewed-by: Sudeep Holla <sudeep.holla@xxxxxxx> Tested-by: Sudeep Holla <sudeep.holla@xxxxxxx> Signed-off-by: Timothy E Baldwin <T.E.Baldwin99@xxxxxxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/90edd33b-6353-1228-791f-0336d94d5f8c@xxxxxxxxxxxxxx Signed-off-by: Will Deacon <will@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm64/kernel/ptrace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -1844,7 +1844,7 @@ int syscall_trace_enter(struct pt_regs * if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) { tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER); - if (!in_syscall(regs) || (flags & _TIF_SYSCALL_EMU)) + if (flags & _TIF_SYSCALL_EMU) return -1; } Patches currently in stable-queue which might be from T.E.Baldwin99@xxxxxxxxxxxxxxxxxxx are queue-5.4/arm64-ptrace-fix-seccomp-of-traced-syscall-1-no_syscall.patch