From b08418b54831255a7e3700d6bf7dfc2bdae25cd7 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Sat, 25 Apr 2020 05:03:06 -0500 Subject: x86/unwind: Prevent false warnings for non-current tasks There's some daring kernel code out there which dumps the stack of another task without first making sure the task is inactive. If the task happens to be running while the unwinder is reading the stack, unusual unwinder warnings can result. There's no race-free way for the unwinder to know whether such a warning is legitimate, so just disable unwinder warnings for all non-current tasks. Reviewed-by: Miroslav Benes Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Andy Lutomirski Cc: Dave Jones Cc: Jann Horn Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Vince Weaver Link: https://lore.kernel.org/r/ec424a2aea1d461eb30cab48a28c6433de2ab784.1587808742.git.jpoimboe@redhat.com --- arch/x86/kernel/dumpstack_64.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/x86/kernel/dumpstack_64.c') diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c index 87b97897a881..460ae7f66818 100644 --- a/arch/x86/kernel/dumpstack_64.c +++ b/arch/x86/kernel/dumpstack_64.c @@ -183,7 +183,8 @@ recursion_check: */ if (visit_mask) { if (*visit_mask & (1UL << info->type)) { - printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n", info->type); + if (task == current) + printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n", info->type); goto unknown; } *visit_mask |= 1UL << info->type; -- cgit v1.2.3