Re: Kernel WARNING at lib/vsprintf.c:2721 while running ftrace kernel selftests

[Steven Rostedt <rostedt@goodmis.org>]

On Tue, 27 Feb 2024 21:38:57 +0530
Sachin Sant <sachinp@linux.ibm.com> wrote:

> This warning was not triggered.

Interesting.

> 
> I have attached .config

This is what I was looking for:

> # CONFIG_PPC_4K_PAGES is not set
> CONFIG_PPC_64K_PAGES=y
> CONFIG_PAGE_SIZE_64KB=y
> CONFIG_PPC_PAGE_SHIFT=16

So the pages are 64K in size. I wonder if this is causing an issue.

Can you apply this, and see if it triggers and if it does, print the line
that has the max size?

-- Steve

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 3e7fa44dc2b2..43e270bf8d78 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -1589,6 +1589,9 @@ static enum print_line_t trace_print_print(struct trace_iterator *iter,
 	struct trace_seq *s = &iter->seq;
 	int max = iter->ent_size - offsetof(struct print_entry, buf);
 
+	if (WARN_ONCE(max < 0 || max > 2000, "MAX OUT OF RANGE %d", max))
+		return TRACE_TYPE_UNHANDLED;
+
 	trace_assign_type(field, iter->ent);
 
 	seq_print_ip_sym(s, field->ip, flags);