From 5475c03fa25f31cfd5f8c7e552f8d10347bbaad9 Mon Sep 17 00:00:00 2001 From: Thomas Bogendoerfer Date: Fri, 17 Jul 2026 13:27:31 +0200 Subject: [PATCH] MIPS: ptrace: Fix syscall skipping via PTRACE_SYSCALL MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit If tracer wanted to skip a syscall return value was always overwritten with -ENOSYS. Fix this by checking against original syscall number and only return -ENOSYS, if it is negative. Fixes: b6318a903d06 ("MIPS/ptrace: Pick up ptrace/seccomp changed syscalls") Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Thomas Bogendoerfer --- arch/mips/kernel/ptrace.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c index 3f4c94c88124..87102a03b6ea 100644 --- a/arch/mips/kernel/ptrace.c +++ b/arch/mips/kernel/ptrace.c @@ -1321,8 +1321,12 @@ long arch_ptrace(struct task_struct *child, long request, */ asmlinkage long syscall_trace_enter(struct pt_regs *regs) { + long syscall; + user_exit(); + syscall = current_thread_info()->syscall; + if (test_thread_flag(TIF_SYSCALL_TRACE)) { if (ptrace_report_syscall_entry(regs)) return -1; @@ -1342,7 +1346,7 @@ asmlinkage long syscall_trace_enter(struct pt_regs *regs) * Negative syscall numbers are mistaken for rejected syscalls, but * won't have had the return value set appropriately, so we do so now. */ - if (current_thread_info()->syscall < 0) + if (syscall < 0) syscall_set_return_value(current, regs, -ENOSYS, 0); return current_thread_info()->syscall; }