From: Jann Horn Date: Tue, 10 Dec 2024 16:32:13 +0000 (+0100) Subject: bpf: Fix UAF via mismatching bpf_prog/attachment RCU flavors X-Git-Tag: v6.13-rc3~9^2~9 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=ef1b808e3b7c;p=thirdparty%2Flinux.git bpf: Fix UAF via mismatching bpf_prog/attachment RCU flavors 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 Suggested-by: Alexei Starovoitov Signed-off-by: Jann Horn Signed-off-by: Andrii Nakryiko Cc: stable@vger.kernel.org Link: https://lore.kernel.org/bpf/20241210-bpf-fix-actual-uprobe-uaf-v1-1-19439849dd44@google.com --- diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 949a3870946c3..a403b05a70913 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2258,6 +2258,13 @@ void perf_event_detach_bpf_prog(struct perf_event *event) 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;