This is a note to let you know that I've just added the patch titled

x86/debug: Handle warnings before the notifier chain, to fix KGDB crash

to the 4.13-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86-debug-handle-warnings-before-the-notifier-chain-to-fix-kgdb-crash.patch and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From b8347c2196492f4e1cccde3d92fda1cc2cc7de7e Mon Sep 17 00:00:00 2001

From: Alexander Shishkin alexander.shishkin@linux.intel.com Date: Mon, 24 Jul 2017 13:04:28 +0300 Subject: x86/debug: Handle warnings before the notifier chain, to fix KGDB crash

From: Alexander Shishkin alexander.shishkin@linux.intel.com

commit b8347c2196492f4e1cccde3d92fda1cc2cc7de7e upstream.

Commit:

9a93848fe787 ("x86/debug: Implement __WARN() using UD0")

turned warnings into UD0, but the fixup code only runs after the notify_die() chain. This is a problem, in particular, with kgdb, which kicks in as if it was a BUG().

Fix this by running the fixup code before the notifier chain in the invalid op handler path.

Signed-off-by: Alexander Shishkin alexander.shishkin@linux.intel.com Tested-by: Ilya Dryomov idryomov@gmail.com Acked-by: Daniel Thompson daniel.thompson@linaro.org Acked-by: Thomas Gleixner tglx@linutronix.de Cc: Jason Wessel jason.wessel@windriver.com Cc: Arjan van de Ven arjan@linux.intel.com Cc: Borislav Petkov bp@alien8.de Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Richard Weinberger richard.weinberger@gmail.com Link: http://lkml.kernel.org/r/20170724100428.19173-1-alexander.shishkin@linux.int... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/x86/kernel/traps.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -221,9 +221,6 @@ do_trap_no_signal(struct task_struct *ts if (fixup_exception(regs, trapnr)) return 0;

- if (fixup_bug(regs, trapnr)) - return 0; - tsk->thread.error_code = error_code; tsk->thread.trap_nr = trapnr; die(str, regs, error_code); @@ -304,6 +301,13 @@ static void do_error_trap(struct pt_regs

RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");

+ /* + * WARN*()s end up here; fix them up before we call the + * notifier chain. + */ + if (!user_mode(regs) && fixup_bug(regs, trapnr)) + return; + if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) != NOTIFY_STOP) { cond_local_irq_enable(regs);

Patches currently in stable-queue which might be from alexander.shishkin@linux.intel.com are

queue-4.13/x86-debug-handle-warnings-before-the-notifier-chain-to-fix-kgdb-crash.patch