FAILED: patch "[PATCH] tracing/synthetic: Allocate one additional element for size" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x c4d6b5438116c184027b2e911c0f2c7c406fb47c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023082710-twisty-automatic-966e@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

c4d6b5438116 ("tracing/synthetic: Allocate one additional element for size") fc1a9dc10129 ("tracing/histogram: Don't use strlen to find length of stacktrace variables") 288709c9f3b0 ("tracing: Allow stacktraces to be saved as histogram variables") 5f2e094ed259 ("tracing: Allow multiple hitcount values in histograms")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c4d6b5438116c184027b2e911c0f2c7c406fb47c Mon Sep 17 00:00:00 2001
From: Sven Schnelle <[email protected]>
Date: Wed, 16 Aug 2023 17:49:28 +0200
Subject: [PATCH] tracing/synthetic: Allocate one additional element for size

While debugging another issue I noticed that the stack trace contains one invalid entry at the end:

<idle>-0 [008] d..4. 26.484201: wake_lat: pid=0 delta=2629976084 000000009cc24024 stack=STACK:
=> __schedule+0xac6/0x1a98
=> schedule+0x126/0x2c0
=> schedule_timeout+0x150/0x2c0
=> kcompactd+0x9ca/0xc20
=> kthread+0x2f6/0x3d8
=> __ret_from_fork+0x8a/0xe8
=> 0x6b6b6b6b6b6b6b6b

This is because the code failed to add the one element containing the number of entries to field_size.

index 80a2a832f857..9897d0bfcab7 100644
@@ -528,7 +528,8 @@ static notrace void trace_event_raw_event_synth(void *__data,
 		str_val = (char *)(long)var_ref_vals[val_idx];
 
 		if (event->dynamic_fields[i]->is_stack) {
-			len = *((unsigned long *)str_val);
+			/* reserve one extra element for size */
+			len = *((unsigned long *)str_val) + 1;
 			len *= sizeof(unsigned long);
 		} else {
 			len = fetch_store_strlen((unsigned long)str_val);