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bpf: Fix UAF via mismatching bpf_prog/attachment RCU flavors

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commit ef1b808e3b 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: 8c7dcb84e3 ("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-v1-1-19439849dd44@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jann Horn
2024-12-10 17:32:13 +01:00
committed by Greg Kroah-Hartman
parent 7415bc5198
commit 9b53d2c2a3
1 changed files with 7 additions and 0 deletions
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kernel/trace/bpf_trace.c
+7
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@@ -2223,6 +2223,13 @@ 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;