From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f47.google.com (mail-pj1-f47.google.com [209.85.216.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3048B368D7C for ; Thu, 25 Jun 2026 01:23:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.47 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782350633; cv=none; b=fZzRDU8W+KFlnkHSFlWJo3Wb7y0bq9pomQ6fey5O4M6cckXOK/YrF3LsFdnXdbAtMm0rG3fSt6nPUJQ8oNV8WwnIHGlAd5k8ktbfWD3pCi+LIb3lEF9COP7du7BsDxZjyfTPBcYZGHM+el7DYXYeDgbuppdZRopVY0BCIwrt6Jo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782350633; c=relaxed/simple; bh=T9SXqfsO/EFq+dYj0i1JvBToxhsvtWDwvs2JRGi+kgM=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Um/S5DwfuPycQkkcF5SgmcMrD7BSRnLuuw38FJWTWdAp4JzLuODAJy2aQYRoMrzuQh/O+9uwr6zOHm7UHoo3thkS0SIMygG9Cyc55NyZ0l52fwG03akeAx1D9aygiuPZIj7odOUKqfbIhkE/rHyLzLDZHAMDNDehehe/EllbdLc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=LfFxJsMV; arc=none smtp.client-ip=209.85.216.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="LfFxJsMV" Received: by mail-pj1-f47.google.com with SMTP id 98e67ed59e1d1-37df0b86a82so229430a91.0 for ; Wed, 24 Jun 2026 18:23:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1782350631; x=1782955431; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=XWrI8sitTaDcWEaHG+ZnIRCNC7VJeTwjUrHgR3uWgo8=; b=LfFxJsMVytxTBnqopl4HTZWKaCw7fr8/yIcl62JXLZeyiL1h1GTWPn2aNQg6tG5cPX 0KbSKI/KMuaptoAM4ts/UomQOSxJ9DMv2gGkSE9CFkgCn4pX2WE/N+TKyFOLho5RUBQk E315W3LdoYVotNiWu71owoXTL+4L8j4NcUnRJhXMP4iYeTkPAFCOjL4gt0UX6+MuSbVR 0O2WkB/lNvQl/0RdIPh0KmEjs1AYw6N7soUEFwZr57REJ6kjt7IRxW3tUjChKBCsrGK7 7L+fVCFNnPf7hPBOpm5+GQbtMaeGmOEqTCZuJHcRIdg/l9+JE6UzbpYnERj/iKMTuVFX ISZg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782350631; x=1782955431; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=XWrI8sitTaDcWEaHG+ZnIRCNC7VJeTwjUrHgR3uWgo8=; b=FRDWQR37bg+VtFxDypV66c1277gmUciXTErA2UTG9heKUWUnK3SMhgPRFu/0RPFYch y0o1SmeTG5lgB5FRVi09EBMtpQJpxJY5hAvViZa4YhEjgXe6nvBNnYbLNi3zbouwicPW Zx/tqq6wvIc98VcdJpdOEFNcy0OCHqng71vEct5d1xam2J3UloQQuSdFPNBB7ihRj4C3 Ja8ZCy9YSgf1GzGTD8UGizMjYtBZOfOUTAfXOQhssbc68Gd7oLQRbceGpaXl9jstev3o BzAZ0cS2DLgUx0ddJ7Oc+KhQuckuV0HepWNpdaCmJSa7zZKUGbD8Xg244HmtXthhpfM1 NFYw== X-Forwarded-Encrypted: i=1; AHgh+RoydQunBuI3Gu/0JLw/14H0Jl6t4IsZp1H7sxIzFucHJCb354IYszjWLA4tDSOWtCuLxTEhTX0vcXJqdc4=@vger.kernel.org X-Gm-Message-State: AOJu0Yz7uJqWf4GzkZFPOQw2VjeyYnLV5tV/iQ6PJaj2A+hS5ZYXnYwU bxoZhhwdkdUuqfLiWw6P5VRGHL18Zv8mWGEv2mpCAmCfILmbMMQZb8Cq X-Gm-Gg: AfdE7ckkIV+xERnhktqEqbh/1u2n+s+s6JZuT1VfkHQMMd3xd+5LsadvIPfsz0xI0bY Bwabf5Be6TOz4KLd9VGjqb3biur8vJQIQyEOh4CJTxJUbfl+jdjKXQRi7lOR5AxCbFT57SZTPts yVowtyIGKRnq1gl2QCBtowK+eagFm++UnG727gkw1wydCyxatMGAYcU/eyoNZwfMs5PxXLljC1u dHqawYPdje7KNDiQ+MgvTFYaeJE0VfXo5BdU+mhMNr3uWvQt1NLml03i7hr4vsgczo6pws4NAkv vOYJMAUaFIqlDQgMPWn3l2jNl8atEYd9Dk4aTzmfQiHC60TTfPm0PrjGnHw6yQW9gkQef0uShvf Iz2URLgIZOMeehjQKjnsVe1H5KxBPCBo+i0znUBhEQJl9mFnjBNaBEFEo8j5GArhh2O+Y2jaCPN zsC3DDvH1saTmQGt/449rWjGHlmH0= X-Received: by 2002:a17:90b:48d0:b0:373:302d:3ce6 with SMTP id 98e67ed59e1d1-37df911f73bmr384288a91.8.1782350631330; Wed, 24 Jun 2026 18:23:51 -0700 (PDT) Received: from online.mioffice.cn ([43.224.245.228]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-37df613b3a2sm158588a91.0.2026.06.24.18.23.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jun 2026 18:23:50 -0700 (PDT) From: Pengfei Zhang To: dsahern@kernel.org, idosch@nvidia.com Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, chenzhangqi@xiaomi.com, baohua@kernel.org, Pengfei Zhang , Pengfei Zhang Subject: [PATCH v2] ipv6: fib6: fix NULL deref in fib6_walk_continue() on multi-batch dump Date: Thu, 25 Jun 2026 09:23:44 +0800 Message-Id: <20260625012344.892480-1-zhangfeionline@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260624171156.822055-1-zhangfeionline@gmail.com> References: <20260624171156.822055-1-zhangfeionline@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Pengfei Zhang inet6_dump_fib() saves its progress in cb->args[1] as a positional index within the current hash chain. Between batches the RTNL lock is released, so a concurrent fib6_new_table() can insert a new table at the chain head, shifting all existing entries. The saved index then lands on a different table, causing fib6_dump_table() to set w->root to the wrong table while w->node still points into the previous one. fib6_walk_continue() dereferences w->node->parent (NULL) and panics: BUG: kernel NULL pointer dereference, address: 0000000000000008 RIP: 0010:fib6_walk_continue+0x6e/0x170 Call Trace: fib6_dump_table.isra.0+0xc5/0x240 inet6_dump_fib+0xf6/0x420 rtnl_dumpit+0x30/0xa0 netlink_dump+0x15b/0x460 netlink_recvmsg+0x1d6/0x2a0 ____sys_recvmsg+0x17a/0x190 Fix by storing tb->tb6_id in cb->args[1] instead of a positional index. On resume, skip entries until the id matches; a concurrent head-insert can never match the saved id, so the walker always resumes on the correct table. Fixes: 1b43af5480c3 ("[IPV6]: Increase number of possible routing tables to 2^32") Signed-off-by: Pengfei Zhang --- net/ipv6/ip6_fib.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index fc95738de..bda492634 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -636,11 +636,11 @@ static int inet6_dump_fib(struct sk_buff *skb, struct netlink_callback *cb) }; const struct nlmsghdr *nlh = cb->nlh; struct net *net = sock_net(skb->sk); - unsigned int e = 0, s_e; struct hlist_head *head; struct fib6_walker *w; struct fib6_table *tb; unsigned int h, s_h; + u32 s_id; int err = 0; rcu_read_lock(); @@ -701,23 +701,22 @@ static int inet6_dump_fib(struct sk_buff *skb, struct netlink_callback *cb) } s_h = cb->args[0]; - s_e = cb->args[1]; + s_id = cb->args[1]; - for (h = s_h; h < FIB6_TABLE_HASHSZ; h++, s_e = 0) { - e = 0; + for (h = s_h; h < FIB6_TABLE_HASHSZ; h++, s_id = 0) { head = &net->ipv6.fib_table_hash[h]; hlist_for_each_entry_rcu(tb, head, tb6_hlist) { - if (e < s_e) - goto next; + if (s_id && tb->tb6_id != s_id) + continue; + s_id = 0; + + cb->args[1] = tb->tb6_id; err = fib6_dump_table(tb, skb, cb); if (err != 0) goto out; -next: - e++; } } out: - cb->args[1] = e; cb->args[0] = h; unlock: -- 2.34.1