tracing: Check field value in hist_field_name()

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: default avatarMark Rutland <mark.rutland@arm.com>
Fixes: c6afad49 ("tracing: Add hist trigger 'sym' and 'sym-offset' modifiers")
Tested-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent e0213434
...@@ -1331,6 +1331,9 @@ static const char *hist_field_name(struct hist_field *field, ...@@ -1331,6 +1331,9 @@ static const char *hist_field_name(struct hist_field *field,
{ {
const char *field_name = ""; const char *field_name = "";
if (WARN_ON_ONCE(!field))
return field_name;
if (level > 1) if (level > 1)
return field_name; return field_name;
......
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