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 F05C7FBEF; Tue, 25 Jun 2024 09:35:29 +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=1719308130; cv=none; b=rbCRgtZflBrWaR3Gb8ndfFF6xqpNyKxvPQV4N+zyKw4f9MSw1ilLAXQFq0lqjpBkDPoOYB5KP6Vodce5qmadKDbP3zjowzhGvL8VFHxZyOBZExKqArjKvwpwnlXR8i02DuUg64hyvP1Rm3wzfcFLlAqkO+UIJaR1gLym6YkOE2k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719308130; c=relaxed/simple; bh=ZLoVhnd6wA/0LdsND8kyM6F3RboxjLBHFuC1/qbJgWM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VK7SvxVBWQn/UgvDTo1lgI8NKWQqoLRdOdj9EHklvQFN0KUEpEewCtBxVC3L1iS0MIYIfpJc4TAs7btZHpSfYlfCecl3wuWoePct5nQuQlBZq0/Uvm1cI2gIczunC8pGVGIPz/Ak9K310MxNCRmQacxNayoJHSA20H3Q7cUqJ/U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=f4uQtlNA; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="f4uQtlNA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 25371C32781; Tue, 25 Jun 2024 09:35:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1719308129; bh=ZLoVhnd6wA/0LdsND8kyM6F3RboxjLBHFuC1/qbJgWM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=f4uQtlNAd1Ol4fzXvfjWQ/r/Zxis3KSDTrxKmL5QEOT8KwgT+Ge2DORoNwE1rQ838 aoX5GFAquLfpTAqkssfSoEPr8+NE9qHkILPvJi5Mm0h1hEFwG6R3ipQGjmYq03MGvG mOjQ9IQIHKsJIKjYq0e7bfUoCPHV/MF00mcxdKPE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+1fa663a2100308ab6eab@syzkaller.appspotmail.com, Alexei Starovoitov , Andrii Nakryiko , Sasha Levin Subject: [PATCH 6.9 017/250] bpf: Avoid kfree_rcu() under lock in bpf_lpm_trie. Date: Tue, 25 Jun 2024 11:29:35 +0200 Message-ID: <20240625085548.711318636@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240625085548.033507125@linuxfoundation.org> References: <20240625085548.033507125@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.9-stable review patch. If anyone has any objections, please let me know. ------------------ 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