Commit c9c26150 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Thomas Gleixner
Browse files

x86/entry: Assert that syscalls are on the right stack 



Now that the entry stack is a full page, it's too easy to regress the
system call entry code and end up on the wrong stack without noticing.
Assert that all system calls (SYSCALL64, SYSCALL32, SYSENTER, and INT80)
are on the right stack and have pt_regs in the right place.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/52059e42bb0ab8551153d012d68f7be18d72ff8e.1593191971.git.luto@kernel.org
parent 009bce1d

arch/x86/entry/common.c

+15 −3
Original line number Diff line number Diff line
@@ -45,6 +45,15 @@ 
#define CREATE_TRACE_POINTS

#include <trace/events/syscalls.h>



/* Check that the stack and regs on entry from user mode are sane. */

static void check_user_regs(struct pt_regs *regs)

{

	if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) {

		WARN_ON_ONCE(!on_thread_stack());

		WARN_ON_ONCE(regs != task_pt_regs(current));

	}

}



#ifdef CONFIG_CONTEXT_TRACKING

/**

 * enter_from_user_mode - Establish state when coming from user mode
@@ -127,9 +136,6 @@ static long syscall_trace_enter(struct pt_regs *regs) 
	unsigned long ret = 0;

	u32 work;



	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))

		BUG_ON(regs != task_pt_regs(current));



	work = READ_ONCE(ti->flags);



	if (work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
@@ -346,6 +352,8 @@ __visible noinstr void do_syscall_64(unsigned long nr, struct pt_regs *regs) 
{

	struct thread_info *ti;



	check_user_regs(regs);



	enter_from_user_mode();

	instrumentation_begin();
@@ -409,6 +417,8 @@ static void do_syscall_32_irqs_on(struct pt_regs *regs) 
/* Handles int $0x80 */

__visible noinstr void do_int80_syscall_32(struct pt_regs *regs)

{

	check_user_regs(regs);



	enter_from_user_mode();

	instrumentation_begin();
@@ -460,6 +470,8 @@ __visible noinstr long do_fast_syscall_32(struct pt_regs *regs) 
					vdso_image_32.sym_int80_landing_pad;

	bool success;



	check_user_regs(regs);



	/*

	 * SYSENTER loses EIP, and even SYSCALL32 needs us to skip forward

	 * so that 'regs->ip -= 2' lands back on an int $0x80 instruction.

CRA Git | Maintained and supported by SUSTech CRA and CCSE