Merge tag 'trace-v5.12-rc5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

05de4538 · Linus Torvalds <[email protected]> · 2021-04-02 08:39:00 -07:00

Pull tracing fix from Steven Rostedt:
 "Fix stack trace entry size to stop showing garbage

  The macro that creates both the structure and the format displayed to
  user space for the stack trace event was changed a while ago to fix
  the parsing by user space tooling. But this change also modified the
  structure used to store the stack trace event. It changed the caller
  array field from [0] to [8].

  Even though the size in the ring buffer is dynamic and can be
  something other than 8 (user space knows how to handle this), the 8
  extra words was not accounted for when reserving the event on the ring
  buffer, and added 8 more entries, due to the calculation of
  "sizeof(*entry) + nr_entries * sizeof(long)", as the sizeof(*entry)
  now contains 8 entries.

  The size of the caller field needs to be subtracted from the size of
  the entry to create the correct allocation size"

* tag 'trace-v5.12-rc5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Fix stack trace event size

Commit: 05de45383bd134fcb2b7d70d35ebb0bb50b5e4aa
Parents: 1678e493 · 9deb193a

Merge commit. Changes below are compared with the first parent: 1678e493.

Changes

1 files changed · +2 −1

File	Status	Add	Del	Content
kernel/trace/trace.c	modified	+2	−1	View file

kernel/trace/trace.c

View file

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index eccb4e1..5c77762 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2984,7 +2984,8 @@ static void __ftrace_trace_stack(struct trace_buffer *buffer,
 
 	size = nr_entries * sizeof(unsigned long);
 	event = __trace_buffer_lock_reserve(buffer, TRACE_STACK,
-					    sizeof(*entry) + size, trace_ctx);
+				    (sizeof(*entry) - sizeof(entry->caller)) + size,
+				    trace_ctx);
 	if (!event)
 		goto out;
 	entry = ring_buffer_event_data(event);