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

[sfrench/cifs-2.6.git] / arch / x86 / entry / common.c

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index bd3f14175193c35515fc003f47d18b528bf77953..ed8ccc820995475c5e301a73501f0a68735a3059 100644 (file)
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -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.