FAILED: patch "[PATCH] bpf,perf: Fix invalid prog_array access in" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-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 <stable@vger.kernel.org>.

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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 978c4486cca5c7b9253d3ab98a88c8e769cb9bbd
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024121506-pancreas-mosaic-0ae0@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From 978c4486cca5c7b9253d3ab98a88c8e769cb9bbd Mon Sep 17 00:00:00 2001
From: Jiri Olsa <jolsa@kernel.org>
Date: Sun, 8 Dec 2024 15:25:07 +0100
Subject: [PATCH] bpf,perf: Fix invalid prog_array access in
 perf_event_detach_bpf_prog

Syzbot reported [1] crash that happens for following tracing scenario:

  - create tracepoint perf event with attr.inherit=1, attach it to the
    process and set bpf program to it
  - attached process forks -> chid creates inherited event

    the new child event shares the parent's bpf program and tp_event
    (hence prog_array) which is global for tracepoint

  - exit both process and its child -> release both events
  - first perf_event_detach_bpf_prog call will release tp_event->prog_array
    and second perf_event_detach_bpf_prog will crash, because
    tp_event->prog_array is NULL

The fix makes sure the perf_event_detach_bpf_prog checks prog_array
is valid before it tries to remove the bpf program from it.

[1] https://lore.kernel.org/bpf/Z1MR6dCIKajNS6nU@krava/T/#m91dbf0688221ec7a7fc95e896a7ef9ff93b0b8ad

Fixes: 0ee288e69d03 ("bpf,perf: Fix perf_event_detach_bpf_prog error handling")
Reported-by: syzbot+2e0d2840414ce817aaac@syzkaller.appspotmail.com
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241208142507.1207698-1-jolsa@kernel.org

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index a403b05a7091..1b8db5aee9d3 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2250,6 +2250,9 @@ void perf_event_detach_bpf_prog(struct perf_event *event)
 		goto unlock;
 
 	old_array = bpf_event_rcu_dereference(event->tp_event->prog_array);
+	if (!old_array)
+		goto put;
+
 	ret = bpf_prog_array_copy(old_array, event->prog, NULL, 0, &new_array);
 	if (ret < 0) {
 		bpf_prog_array_delete_safe(old_array, event->prog);
@@ -2258,6 +2261,7 @@ void perf_event_detach_bpf_prog(struct perf_event *event)
 		bpf_prog_array_free_sleepable(old_array);
 	}
 
+put:
 	/*
 	 * It could be that the bpf_prog is not sleepable (and will be freed
 	 * via normal RCU), but is called from a point that supports sleepable