From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 461EE278156 for ; Mon, 18 May 2026 02:11:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779070263; cv=none; b=MoVZ+qOM1VA3Ytvm9WFKqpQqcFhOffYbUJ2GWGZQap6HQLEJXZ/utFZ12EVIaROzmvz3bQlKihXEChuNJmy37Qpw65r9qQLP+1YQuCxUqvOVjd2YOg9OHnorbzI1fFcg7Yh/druIUXiJU7XMnArSkOp35Jeh82UIdHnGgAdMOLk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779070263; c=relaxed/simple; bh=NcKAeOojO2nQci9Kq0VxvbCF5J7wh9vhBALrTNs4w6s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kBAjqvjQy+FrGocTodDFlRF4sPN7H4xkKk1t2DGUm2+HqFldPHtMzmUMSDn/K3WWqtXgg9H8ILOdgtdDl2xfFuldncNzszUMgPM1gX6RadvyDz3pLqzWWCPUQ0Vz0MKLxMe58DykogXTdwpLgoYs6snsAAaKLWfJVS408JVHdaA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KgzwK7m+; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KgzwK7m+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 527EFC2BCB0; Mon, 18 May 2026 02:11:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1779070262; bh=NcKAeOojO2nQci9Kq0VxvbCF5J7wh9vhBALrTNs4w6s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KgzwK7m+QH0wtqmdoYmujRj4YQYVtLLRAxUDUnSkq9ZqTMmqzzpDJvckUtoh6MhOQ 6huShoWXUFztftFGJhtv/QTNflt161UWQxgDhCvpNyPqYfyoeWNLeQcezhM/TjBFTf TOzRA0HNyXpOWwYx/Adj+A1C32f2zLFhU7Y0NpaD6QN8gGJR1FpemCh0MffqCZ2IeT b5tFj7jDmSG3niYjP9BlOr+xlyjKkj2uSXxIwws5qPXqaqni7KQy+eKG7ClpOf9meN hZcW5saMqew8SwUGmY1i/UWtHgAL+UF2PWeanzsPkMD5+RFDnBrEp2q03eJ9KENmIB ABKrJY4AxT8TQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Tejun Heo , Chris Mason , Andrea Righi , Sasha Levin Subject: [PATCH 6.18.y] sched_ext: Guard scx_dsq_move() against NULL kit->dsq after failed iter_new Date: Sun, 17 May 2026 22:11:00 -0400 Message-ID: <20260518021100.535042-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026051201-cupping-demotion-047d@gregkh> References: <2026051201-cupping-demotion-047d@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Tejun Heo [ Upstream commit 4fda9f0e7c950da4fe03cedeb2ac818edf5d03e9 ] bpf_iter_scx_dsq_new() clears kit->dsq on failure and bpf_iter_scx_dsq_{next,destroy}() guard against that. scx_dsq_move() doesn't - it dereferences kit->dsq immediately, so a BPF program that calls scx_bpf_dsq_move[_vtime]() after a failed iter_new oopses the kernel. Return false if kit->dsq is NULL. Fixes: 4c30f5ce4f7a ("sched_ext: Implement scx_bpf_dispatch[_vtime]_from_dsq()") Cc: stable@vger.kernel.org # v6.12+ Reported-by: Chris Mason Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi [ dropped upstream `sch = src_dsq->sched` reordering since stable initializes `sch` from `scx_root` instead ] Signed-off-by: Sasha Levin --- kernel/sched/ext.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 177bbf31116d0..5e989409c7715 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -5650,6 +5650,14 @@ static bool scx_dsq_move(struct bpf_iter_scx_dsq_kern *kit, bool in_balance; unsigned long flags; + /* + * The verifier considers an iterator slot initialized on any + * KF_ITER_NEW return, so a BPF program may legally reach here after + * bpf_iter_scx_dsq_new() failed and left @kit->dsq NULL. + */ + if (unlikely(!src_dsq)) + return false; + if (!scx_kf_allowed_if_unlocked() && !scx_kf_allowed(sch, SCX_KF_DISPATCH)) return false; -- 2.53.0