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 F187B15FA68; Mon, 27 May 2024 14:12:22 +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=1716819143; cv=none; b=d2Ta3v+mUsK1ePcfwxX6875+1lehEcQiDE/nwDar6bjQMJ7TCrZGqEWG2zr0yCxQR+HaR1INRu325A5DZ47zXFwsS//6T5K+OAwCuFhgRpPLjMexx7lnHezmTXRefKXPLq/8VtI/jwEPIeclidLPAKPErzvd1+54fkhjAeSU58I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716819143; c=relaxed/simple; bh=HrTEdUzVuB12p0SLte4yR5sIXNZvCTC49ZZH/0a3r8o=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CPgW371rU8wNKzlixRtIBfaXvhHZfRTIf3BP0RKf8PVna7qy560beEcQfraaW4YgihZ/s7N6uCiAT5A8rVszgRlfLnvIXq+RNuqRtDrc6aAFV0SOcptCBAZBDvK3h7aEdF1uBGgxJ9QJsSstYg7cPT2vmbOIDJRa+xyqDBLntkI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=uDXLWkD1; 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="uDXLWkD1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B3E51C2BBFC; Mon, 27 May 2024 14:12:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1716819142; bh=HrTEdUzVuB12p0SLte4yR5sIXNZvCTC49ZZH/0a3r8o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uDXLWkD1nmVnKXp9ts/EVvNEYh1mEPHky2W+KngWs3JRsJkNIWPUew6yZRxrybl8B LdPY4/yfTxj1o9ZBeJegJ9WCKPnUKL4O4zYcricgmHlkwHSXTQz7lBHlPcepUP4Hm2 38wdT6p1ToPz5cpQFY0CKpDn82ABIa0zsqufnYzC4a/PwVV0E4lYbFa0nJeTnyuHF6 WqlsNkiEV2BbqXU+ppP2d9rZiS/28peJqL0wf7SKgFNtubqQ/MZ2xoAD08auyQPMv8 C4Ex3jxRmKAakheC/q5A9aF8hIFE+aYY10OL6XflJtgVGh/WBGlHvLoYBB1jQX1JpT 4lbcyfC4g5mWA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Alexei Starovoitov , syzbot+1fa663a2100308ab6eab@syzkaller.appspotmail.com, Andrii Nakryiko , Sasha Levin , daniel@iogearbox.net, bpf@vger.kernel.org Subject: [PATCH AUTOSEL 6.9 04/35] bpf: Avoid kfree_rcu() under lock in bpf_lpm_trie. Date: Mon, 27 May 2024 10:11:09 -0400 Message-ID: <20240527141214.3844331-4-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240527141214.3844331-1-sashal@kernel.org> References: <20240527141214.3844331-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.9.2 Content-Transfer-Encoding: 8bit From: Alexei Starovoitov [ Upstream commit 59f2f841179aa6a0899cb9cf53659149a35749b7 ] syzbot reported the following lock sequence: cpu 2: grabs timer_base lock spins on bpf_lpm lock cpu 1: grab rcu krcp lock spins on timer_base lock cpu 0: grab bpf_lpm lock spins on rcu krcp lock bpf_lpm lock can be the same. timer_base lock can also be the same due to timer migration. but rcu krcp lock is always per-cpu, so it cannot be the same lock. Hence it's a false positive. To avoid lockdep complaining move kfree_rcu() after spin_unlock. Reported-by: syzbot+1fa663a2100308ab6eab@syzkaller.appspotmail.com Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20240329171439.37813-1-alexei.starovoitov@gmail.com Signed-off-by: Sasha Levin --- kernel/bpf/lpm_trie.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c index 050fe1ebf0f7d..d0febf07051ed 100644 --- a/kernel/bpf/lpm_trie.c +++ b/kernel/bpf/lpm_trie.c @@ -308,6 +308,7 @@ static long trie_update_elem(struct bpf_map *map, { struct lpm_trie *trie = container_of(map, struct lpm_trie, map); struct lpm_trie_node *node, *im_node = NULL, *new_node = NULL; + struct lpm_trie_node *free_node = NULL; struct lpm_trie_node __rcu **slot; struct bpf_lpm_trie_key_u8 *key = _key; unsigned long irq_flags; @@ -382,7 +383,7 @@ static long trie_update_elem(struct bpf_map *map, trie->n_entries--; rcu_assign_pointer(*slot, new_node); - kfree_rcu(node, rcu); + free_node = node; goto out; } @@ -429,6 +430,7 @@ static long trie_update_elem(struct bpf_map *map, } spin_unlock_irqrestore(&trie->lock, irq_flags); + kfree_rcu(free_node, rcu); return ret; } @@ -437,6 +439,7 @@ static long trie_update_elem(struct bpf_map *map, static long trie_delete_elem(struct bpf_map *map, void *_key) { struct lpm_trie *trie = container_of(map, struct lpm_trie, map); + struct lpm_trie_node *free_node = NULL, *free_parent = NULL; struct bpf_lpm_trie_key_u8 *key = _key; struct lpm_trie_node __rcu **trim, **trim2; struct lpm_trie_node *node, *parent; @@ -506,8 +509,8 @@ static long trie_delete_elem(struct bpf_map *map, void *_key) else rcu_assign_pointer( *trim2, rcu_access_pointer(parent->child[0])); - kfree_rcu(parent, rcu); - kfree_rcu(node, rcu); + free_parent = parent; + free_node = node; goto out; } @@ -521,10 +524,12 @@ static long trie_delete_elem(struct bpf_map *map, void *_key) rcu_assign_pointer(*trim, rcu_access_pointer(node->child[1])); else RCU_INIT_POINTER(*trim, NULL); - kfree_rcu(node, rcu); + free_node = node; out: spin_unlock_irqrestore(&trie->lock, irq_flags); + kfree_rcu(free_parent, rcu); + kfree_rcu(free_node, rcu); return ret; } -- 2.43.0