From: Woraphat Khiaodaeng Date: Fri, 17 Jul 2026 15:45:37 +0000 (+0700) Subject: io_uring/bpf-ops: reject re-registration of an already-bound ops X-Git-Tag: v7.2-rc4~3^2 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=3afc64c61ce906a04f073ca350b46de10e8302f9;p=thirdparty%2Flinux.git io_uring/bpf-ops: reject re-registration of an already-bound ops io_install_bpf() only rejects a second registration on the ctx side (ctx->bpf_ops) and sets the per-map back-pointer ops->priv unconditionally. The struct_ops link path never advances a map past BPF_STRUCT_OPS_STATE_READY, so the same io_uring_bpf_ops map can be registered more than once, and bpf_io_reg() re-resolves the target ring via fget(ops->ring_fd) on every call. A caller can therefore point the same ring_fd at a different io_ring_ctx between two BPF_LINK_CREATE calls. The second registration passes the ctx->bpf_ops check (the new ctx has none) and overwrites ops->priv, orphaning the first ctx. Teardown (io_eject_bpf()/bpf_io_unreg()) only reaches a ctx through ops->priv, so the orphaned ctx is never torn down: its ctx->loop_step keeps pointing into the struct_ops trampoline, which is freed once the map is gone. A later io_uring_enter() on the orphaned ring then calls the dangling ctx->loop_step from io_run_loop() -- a use-after-free of freed executable memory, reachable by a task with CAP_BPF + CAP_PERFMON. Reject registration when ops->priv is already set, as hid_bpf_reg() does for its struct_ops. Cc: stable@vger.kernel.org Fixes: 98f37634b12b ("io_uring/bpf-ops: implement bpf ops registration") Signed-off-by: Woraphat Khiaodaeng Reviewed-by: Gabriel Krisman Bertazi Reviewed-by: Pavel Begunkov Link: https://patch.msgid.link/20260717154537.129736-1-worapat.kd2@gmail.com Signed-off-by: Jens Axboe --- diff --git a/io_uring/bpf-ops.c b/io_uring/bpf-ops.c index 5a50f0675fe5..cf2bd068e331 100644 --- a/io_uring/bpf-ops.c +++ b/io_uring/bpf-ops.c @@ -168,6 +168,8 @@ static int io_install_bpf(struct io_ring_ctx *ctx, struct io_uring_bpf_ops *ops) if (ctx->bpf_ops) return -EBUSY; + if (ops->priv) + return -EBUSY; if (WARN_ON_ONCE(!ops->loop_step)) return -EINVAL;