Re: Kernel WARNING at lib/vsprintf.c:2721 while running ftrace kernel selftests
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2024-02-27 17:07:13
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
On Tue, 27 Feb 2024 11:56:14 -0500 Steven Rostedt [off-list ref] wrote:
On Tue, 27 Feb 2024 22:08:18 +0530 Sachin Sant [off-list ref] wrote:quoted
quoted
Can you apply this, and see if it triggers and if it does, print the line that has the max size?With this I see following trace [ 61.327138] ------------[ cut here ]------------ [ 61.327159] MAX OUT OF RANGE 63492Well I guess there you have it ;-) vsprintf() doesn't like a precision of 63492! I'll look to see what the best way to deal with this is.
Does this fix it? -- Steve
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ff0b0a999171..e0840b94f1a2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c@@ -6882,7 +6882,9 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, /* Used in tracing_mark_raw_write() as well */ #define FAULTED_STR "<faulted>" #define FAULTED_SIZE (sizeof(FAULTED_STR) - 1) /* '\0' is already accounted for */ - +#ifndef SHORT_MAX +#define SHORT_MAX ((1<<15) - 1) +#endif if (tracing_disabled) return -EINVAL;
@@ -6900,6 +6902,16 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, if (cnt < FAULTED_SIZE) size += FAULTED_SIZE - cnt; + /* + * trace_print_print() uses vsprintf() to determine the size via + * the precision format "%*.s" which can not be greater than + * a signed short. + */ + if (size > SHORT_MAX) { + cnt -= size - SHORT_MAX; + goto again; + } + if (size > TRACE_SEQ_BUFFER_SIZE) { cnt -= size - TRACE_SEQ_BUFFER_SIZE; goto again;