This is a note to let you know that I've just added the patch titled
tracing: Fix trace_check_vprintf() when tp_printk is used
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tracing-fix-trace_check_vprintf-when-tp_printk-is-us.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 1cb1fb29e883574da203a00e0a910f8601e912e8
Author: Steven Rostedt <rostedt@xxxxxxxxxxx>
Date: Thu Oct 3 10:49:25 2024 -0400
tracing: Fix trace_check_vprintf() when tp_printk is used
[ 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>
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;
