6.6-stable review patch. If anyone has any objections, please let me know.
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From: Jann Horn jannh@google.com
commit ef1b808e3b7c98612feceedf985c2fbbeb28f956 upstream.
Uprobes always use bpf_prog_run_array_uprobe() under tasks-trace-RCU protection. But it is possible to attach a non-sleepable BPF program to a uprobe, and non-sleepable BPF programs are freed via normal RCU (see __bpf_prog_put_noref()). This leads to UAF of the bpf_prog because a normal RCU grace period does not imply a tasks-trace-RCU grace period.
Fix it by explicitly waiting for a tasks-trace-RCU grace period after removing the attachment of a bpf_prog to a perf_event.
Fixes: 8c7dcb84e3b7 ("bpf: implement sleepable uprobes by chaining gps") Suggested-by: Andrii Nakryiko andrii@kernel.org Suggested-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Jann Horn jannh@google.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Cc: stable@vger.kernel.org Link: https://lore.kernel.org/bpf/20241210-bpf-fix-actual-uprobe-uaf-v1-1-19439849... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/trace/bpf_trace.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2224,6 +2224,13 @@ void perf_event_detach_bpf_prog(struct p bpf_prog_array_free_sleepable(old_array); }
+ /* + * 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 + * programs and uses tasks-trace-RCU. + */ + synchronize_rcu_tasks_trace(); + bpf_prog_put(event->prog); event->prog = NULL;