From: "Steven Rostedt (Google)" rostedt@goodmis.org

The function hist_field_name() cannot handle being passed a NULL field parameter. It should never be NULL, but due to a previous bug, NULL was passed to the function and the kernel crashed due to a NULL dereference. Mark Rutland reported this to me on IRC.

The bug was fixed, but to prevent future bugs from crashing the kernel, check the field and add a WARN_ON() if it is NULL.

Link: https://lkml.kernel.org/r/20230302020810.762384440@goodmis.org

Cc: stable@vger.kernel.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Andrew Morton akpm@linux-foundation.org Reported-by: Mark Rutland mark.rutland@arm.com Fixes: c6afad49d127f ("tracing: Add hist trigger 'sym' and 'sym-offset' modifiers") Tested-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org --- kernel/trace/trace_events_hist.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 6e8ab726a7b5..486cca3c2b75 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -1331,6 +1331,9 @@ static const char *hist_field_name(struct hist_field *field, { const char *field_name = "";

+ if (WARN_ON_ONCE(!field)) + return field_name; + if (level > 1) return field_name;