Commit 095fe489 authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google)
Browse files

tracing: Limit trace_marker writes to just 4K 

Limit the max print event of trace_marker to just 4K string size. This must
also be less than the amount that can be held by a trace_seq along with
the text that is before the output (like the task name, PID, CPU, state,
etc). As trace_seq is made to handle large events (some greater than 4K).
Make the max size of a trace_marker write event be 4K which is guaranteed
to fit in the trace_seq buffer.

Link: https://lore.kernel.org/linux-trace-kernel/20240304223433.4ba47dff@gandalf.local.home



Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 6f42249f

kernel/trace/trace.c

+5 −5
Original line number Diff line number Diff line
@@ -7293,6 +7293,8 @@ tracing_free_buffer_release(struct inode *inode, struct file *filp) 
	return 0;

}



#define TRACE_MARKER_MAX_SIZE		4096



static ssize_t

tracing_mark_write(struct file *filp, const char __user *ubuf,

					size_t cnt, loff_t *fpos)
@@ -7320,6 +7322,9 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, 
	if ((ssize_t)cnt < 0)

		return -EINVAL;



	if (cnt > TRACE_MARKER_MAX_SIZE)

		cnt = TRACE_MARKER_MAX_SIZE;



	meta_size = sizeof(*entry) + 2;  /* add '\0' and possible '\n' */

 again:

	size = cnt + meta_size;
@@ -7328,11 +7333,6 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, 
	if (cnt < FAULTED_SIZE)

		size += FAULTED_SIZE - cnt;



	if (size > TRACE_SEQ_BUFFER_SIZE) {

		cnt -= size - TRACE_SEQ_BUFFER_SIZE;

		goto again;

	}



	buffer = tr->array_buffer.buffer;

	event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,

					    tracing_gen_ctx());