[GIT pull] objtool/urgent for v5.7-rc6

[Thomas Gleixner]

Linus,

please pull the latest objtool/urgent branch from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 
objtool-urgent-2020-05-17

up to:  71c95825289f: x86/unwind/orc: Fix error handling in __unwind_start()


A single bugfix for the ORC unwinder to ensure that the error flag which
tells the unwinding code whether a stack trace can be trusted or not is
always set correctly. This was messed up by a couple of changes in the
recent past.

Thanks,

        tglx

------------------>
Josh Poimboeuf (1):
      x86/unwind/orc: Fix error handling in __unwind_start()


 arch/x86/kernel/unwind_orc.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 5b0bd8581fe6..fa79e4227d3d 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -617,23 +617,23 @@ EXPORT_SYMBOL_GPL(unwind_next_frame);
 void __unwind_start(struct unwind_state *state, struct task_struct *task,
                    struct pt_regs *regs, unsigned long *first_frame)
 {
-       if (!orc_init)
-               goto done;
-
        memset(state, 0, sizeof(*state));
        state->task = task;
 
+       if (!orc_init)
+               goto err;
+
        /*
         * Refuse to unwind the stack of a task while it's executing on another
         * CPU.  This check is racy, but that's ok: the unwinder has other
         * checks to prevent it from going off the rails.
         */
        if (task_on_another_cpu(task))
-               goto done;
+               goto err;
 
        if (regs) {
                if (user_mode(regs))
-                       goto done;
+                       goto the_end;
 
                state->ip = regs->ip;
                state->sp = regs->sp;
@@ -666,6 +666,7 @@ void __unwind_start(struct unwind_state *state, struct 
task_struct *task,
                 * generate some kind of backtrace if this happens.
                 */
                void *next_page = (void *)PAGE_ALIGN((unsigned long)state->sp);
+               state->error = true;
                if (get_stack_info(next_page, state->task, &state->stack_info,
                                   &state->stack_mask))
                        return;
@@ -691,8 +692,9 @@ void __unwind_start(struct unwind_state *state, struct 
task_struct *task,
 
        return;
 
-done:
+err:
+       state->error = true;
+the_end:
        state->stack_info.type = STACK_TYPE_UNKNOWN;
-       return;
 }
 EXPORT_SYMBOL_GPL(__unwind_start);