Commit 9ddcb87b authored May 10, 2021 by H. Peter Anvin Committed by Ingo Molnar May 12, 2021

x86/regs: Syscall_get_nr() returns -1 for a non-system call



syscall_get_nr() is defined to return -1 for a non-system call or a
ptrace/seccomp restart; not just any arbitrary number. See comment in
<asm-generic/syscall.h> for the official definition of this function.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210510185316.3307264-7-hpa@zytor.com

parent 29e97589

arch/x86/kernel/ptrace.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -911,7 +911,7 @@ static int putreg32(struct task_struct *child, unsigned regno, u32 value)
		* syscall with TS_COMPAT still set.
		*/
		regs->orig_ax = value;
		if (syscall_get_nr(child, regs) >= 0)
		if (syscall_get_nr(child, regs) != -1)
		child->thread_info.status \|= TS_I386_REGS_POKED;
		break;

arch/x86/kernel/signal.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -713,7 +713,7 @@ handle_signal(struct ksignal ksig, struct pt_regs regs)
		save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);

		/* Are we from a system call? */
		if (syscall_get_nr(current, regs) >= 0) {
		if (syscall_get_nr(current, regs) != -1) {
		/* If so, check system call restarting.. */
		switch (syscall_get_error(current, regs)) {
		case -ERESTART_RESTARTBLOCK:
		@@ -793,7 +793,7 @@ void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal)
		}

		/* Did we come from a system call? */
		if (syscall_get_nr(current, regs) >= 0) {
		if (syscall_get_nr(current, regs) != -1) {
		/* Restart the system call - no handlers present */
		switch (syscall_get_error(current, regs)) {
		case -ERESTARTNOHAND: