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[2a03:2880:30ff:4::face:b00c]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a9ee0dc5db6sm76795966b.119.2024.11.07.03.03.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Nov 2024 03:03:09 -0800 (PST) From: Breno Leitao Date: Thu, 07 Nov 2024 03:02:55 -0800 Subject: [PATCH net] ipmr: Fix access to mfc_cache_list without lock held Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20241107-ipmr_rcu-v1-1-ad0cba8dffed@debian.org> X-B4-Tracking: v=1; b=H4sIAF+eLGcC/x3MWwqDMBAF0K0M99tAJtiq2UqR4mPU+TCViS2Cu HehZwHnRBZTyYh0wuSnWT8JkbggDEuXZnE6IhKCDyWzr5xuq71t+LrQ8Fg/Su97fqIgbCaTHv/ qhSQ72uu6AbIhanxfAAAA X-Change-ID: 20241107-ipmr_rcu-291d85400b16 To: "David S. Miller" , David Ahern , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: David Ahern , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Breno Leitao X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=2226; i=leitao@debian.org; h=from:subject:message-id; bh=3ErXnkzPXHXYk1o/fqIsJm8Zuq6K3DTzluGq+w0yz4Q=; b=owEBbQKS/ZANAwAIATWjk5/8eHdtAcsmYgBnLJ5s2DLNLfVUR5XEhUtDtpUR0i8TR+SgzDIQh rPcWOtAt/qJAjMEAAEIAB0WIQSshTmm6PRnAspKQ5s1o5Of/Hh3bQUCZyyebAAKCRA1o5Of/Hh3 bRTQEACMBDVbyND6f42JQfVgt2FLPK8ak5R8Dxg/QqrqDNjJcmVyRAVbAAbOPgMwGjae9KjHmPe jaHUEuIPLmJcZ99SgtoIHknpOfaG/hz3qRIfMTZc8WPT1wKGWZAsdA3YG9RFEmMa1Ia5ZHb4Cxq 7dT+1DMdKwUFoIbKHer5IBHoExsns6F5s2KdHnL8NzOF1b/HPjf8VcSFPIh9O10i4r/17FyYWS9 W2pt5kDxNs5CsBPuPNusJ6cES6b0qE16oGIxrJmmh3HpcMENiPhBDxZGj+M26YZZc9uGrzvX38Z 6/DqPq3IGM7EMkHKc9IX4Wj0K3IyeuSsyJEm8ibs0iVUCXF3i4jid87xBxxklc3HmjuRzL+75Mk 8ZReM5HAMiam7l1mAfbIlynATlRjogNM/Zja3aVFexoPyV0qIFD3rb8gDLJJN+Vo3dqg4COPD4N WFVq0bd5qofmKLilMSCOfcYISBtjFYfY/BRJoPdIJ1TtJY7d5ks4tli2H9xU7fmScshtgAO4z0m Je9j02WfL+DyOuK5isWSMV7mToQbAcAEHycVfZnqnnjH2oJH5W+0aT2uSFMtjNefSeBIODq36Lg OgxmIv1WKlKvwJIRTMYUY3ujIAvvJTvnKhLewHUX4Cbs6vn30qFmuVcRhMFG7UdXtUSGlRNPg2W rMTnORCueQ5AJWA== X-Developer-Key: i=leitao@debian.org; a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D Accessing `mr_table->mfc_cache_list` is protected by an RCU lock. In the following code flow, the lock is not held, causing the following error when `RCU_PROVE` is not held. 6.12.0-rc5-kbuilder-01145-gbac17284bdcb #33 Tainted: G E N ----------------------------- net/ipv4/ipmr_base.c:313 RCU-list traversed in non-reader section!! rcu_scheduler_active =3D 2, debug_locks =3D 1 2 locks held by RetransmitAggre/3519: #0: ffff88816188c6c0 (nlk_cb_mutex-ROUTE){+.+.}-{3:3}, at: __netlink_= dump_start+0x8a/0x290 #1: ffffffff83fcf7a8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_dumpit+0x6b/0= x90 stack backtrace: lockdep_rcu_suspicious mr_table_dump ipmr_rtm_dumproute rtnl_dump_all rtnl_dumpit netlink_dump __netlink_dump_start rtnetlink_rcv_msg netlink_rcv_skb netlink_unicast netlink_sendmsg Fix accessing `mfc_cache_list` without holding the RCU read lock. Adds `rcu_read_lock()` and `rcu_read_unlock()` around `mr_table_dump()` to prevent RCU-list traversal in non-reader section. Since `mr_table_dump()` is the only function that touches the list, that might be the only critical section in `ipmr_rtm_dumproute()` that needs to be protected in ipmr_rtm_dumproute(). Signed-off-by: Breno Leitao Fixes: cb167893f41e ("net: Plumb support for filtering ipv4 and ipv6 multic= ast route dumps") --- net/ipv4/ipmr.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c index 089864c6a35eec146a1ba90c22d79245f8e48158..bb855f32f328024f384a2fa58f4= 2fc227705206e 100644 --- a/net/ipv4/ipmr.c +++ b/net/ipv4/ipmr.c @@ -2612,8 +2612,10 @@ static int ipmr_rtm_dumproute(struct sk_buff *skb, s= truct netlink_callback *cb) NL_SET_ERR_MSG(cb->extack, "ipv4: MR table does not exist"); return -ENOENT; } + rcu_read_lock(); err =3D mr_table_dump(mrt, skb, cb, _ipmr_fill_mroute, &mfc_unres_lock, &filter); + rcu_read_unlock(); return skb->len ? : err; } =20 --- base-commit: 25d70702142ac2115e75e01a0a985c6ea1d78033 change-id: 20241107-ipmr_rcu-291d85400b16 Best regards, --=20 Breno Leitao