6.1-stable review patch. If anyone has any objections, please let me know.
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From: Jiri Olsa jolsa@kernel.org
commit 978c4486cca5c7b9253d3ab98a88c8e769cb9bbd upstream.
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/#m91dbf0688221ec7a7fc95...
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/trace/bpf_trace.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2180,6 +2180,9 @@ void perf_event_detach_bpf_prog(struct p 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); @@ -2188,6 +2191,7 @@ void perf_event_detach_bpf_prog(struct p 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