6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Steven Rostedt <rostedt@xxxxxxxxxxx> [ Upstream commit 50a3242d84ee1625b0bfef29b95f935958dccfbe ] When the tp_printk kernel command line is used, the trace events go directly to printk(). It is still checked via the trace_check_vprintf() function to make sure the pointers of the trace event are legit. The addition of reading buffers from previous boots required adding a delta between the addresses of the previous boot and the current boot so that the pointers in the old buffer can still be used. But this required adding a trace_array pointer to acquire the delta offsets. The tp_printk code does not provide a trace_array (tr) pointer, so when the offsets were examined, a NULL pointer dereference happened and the kernel crashed. If the trace_array does not exist, just default the delta offsets to zero, as that also means the trace event is not being read from a previous boot. Link: https://lore.kernel.org/all/Zv3z5UsG_jsO9_Tb@xxxxxxxxxxxxxxxxxx/ Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> Link: https://lore.kernel.org/20241003104925.4e1b1fd9@xxxxxxxxxxxxxxxxxx Fixes: 07714b4bb3f98 ("tracing: Handle old buffer mappings for event strings and functions") Reported-by: Alison Schofield <alison.schofield@xxxxxxxxx> Tested-by: Alison Schofield <alison.schofield@xxxxxxxxx> Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> Stable-dep-of: afd2627f727b ("tracing: Check "%s" dereference via the field and not the TP_printk format") Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- kernel/trace/trace.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 2a45efc4e417..addc1b326c79 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3858,8 +3858,8 @@ static void test_can_verify(void) void trace_check_vprintf(struct trace_iterator *iter, const char *fmt, va_list ap) { - long text_delta = iter->tr->text_delta; - long data_delta = iter->tr->data_delta; + long text_delta = 0; + long data_delta = 0; const char *p = fmt; const char *str; bool good; @@ -3871,6 +3871,17 @@ void trace_check_vprintf(struct trace_iterator *iter, const char *fmt, if (static_branch_unlikely(&trace_no_verify)) goto print; + /* + * When the kernel is booted with the tp_printk command line + * parameter, trace events go directly through to printk(). + * It also is checked by this function, but it does not + * have an associated trace_array (tr) for it. + */ + if (iter->tr) { + text_delta = iter->tr->text_delta; + data_delta = iter->tr->data_delta; + } + /* Don't bother checking when doing a ftrace_dump() */ if (iter->fmt == static_fmt_buf) goto print; -- 2.39.5
