tracing: Check field value in hist_field_name()

commit afe8943e3ea46cdab497549b235ba28adf3ecfad upstream.

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: 64363d35e3295 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index da3bfe8625d9610990d8ae85f2da3cfc35a96e2a..e3df03cdecbcb6e5d4670cff863c6b57ee38ea60 100644 (file)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1330,6 +1330,9 @@ 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;