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

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Date:   Sun, 17 May 2020 10:04:20 -0000
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [GIT pull] objtool/urgent for v5.7-rc6

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);