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bpf,perf: Fix invalid prog_array access in perf_event_detach_bpf_prog

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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
This commit is contained in:
Jiri Olsa 2024-12-08 15:25:07 +01:00 committed by Andrii Nakryiko
parent ef1b808e3b
commit 978c4486cc
1 changed files with 4 additions and 0 deletions
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4
kernel/trace/bpf_trace.c
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@ -2250,6 +2250,9 @@ void perf_event_detach_bpf_prog(struct perf_event *event)
goto unlock; goto unlock;
old_array = bpf_event_rcu_dereference(event->tp_event->prog_array); 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); ret = bpf_prog_array_copy(old_array, event->prog, NULL, 0, &new_array);
if (ret < 0) { if (ret < 0) {
bpf_prog_array_delete_safe(old_array, event->prog); 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); bpf_prog_array_free_sleepable(old_array);
} }
put:
/* /*
* It could be that the bpf_prog is not sleepable (and will be freed * 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 * via normal RCU), but is called from a point that supports sleepable