This is a note to let you know that I've just added the patch titled
tracing: Check length before giving out the filter buffer
to the 5.10-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-check-length-before-giving-out-the-filter-buffer.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b220c049d5196dd94d992dd2dc8cba1a5e6123bf Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
Date: Wed, 10 Feb 2021 11:53:22 -0500
Subject: tracing: Check length before giving out the filter buffer
From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
commit b220c049d5196dd94d992dd2dc8cba1a5e6123bf upstream.
When filters are used by trace events, a page is allocated on each CPU and
used to copy the trace event fields to this page before writing to the ring
buffer. The reason to use the filter and not write directly into the ring
buffer is because a filter may discard the event and there's more overhead
on discarding from the ring buffer than the extra copy.
The problem here is that there is no check against the size being allocated
when using this page. If an event asks for more than a page size while being
filtered, it will get only a page, leading to the caller writing more that
what was allocated.
Check the length of the request, and if it is more than PAGE_SIZE minus the
header default back to allocating from the ring buffer directly. The ring
buffer may reject the event if its too big anyway, but it wont overflow.
Link: https://lore.kernel.org/ath10k/1612839593-2308-1-git-send-email-wgong@xxxxxxxxxxxxxx/
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 0fc1b09ff1ff4 ("tracing: Use temp buffer when filtering events")
Reported-by: Wen Gong <wgong@xxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2745,7 +2745,7 @@ trace_event_buffer_lock_reserve(struct t
(entry = this_cpu_read(trace_buffered_event))) {
/* Try to use the per cpu buffer first */
val = this_cpu_inc_return(trace_buffered_event_cnt);
- if (val == 1) {
+ if ((len < (PAGE_SIZE - sizeof(*entry))) && val == 1) {
trace_event_setup(entry, type, flags, pc);
entry->array[0] = len;
return entry;
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-5.10/tracing-do-not-count-ftrace-events-in-top-level-enable-output.patch
queue-5.10/tracing-check-length-before-giving-out-the-filter-buffer.patch
