Re: [PATCH 5.10 104/157] mptcp: put subflow sock on connect error
From: Sasha Levin <sashal@kernel.org>
Date: 2021-03-24 14:29:39
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On Wed, Mar 24, 2021 at 10:22:29AM +0100, Greg Kroah-Hartman wrote:
On Wed, Mar 24, 2021 at 10:04:12AM +0100, Florian Westphal wrote:quoted
Naresh Kamboju [off-list ref] wrote:quoted
On Mon, 22 Mar 2021 at 18:15, Greg Kroah-Hartman [off-list ref] wrote:quoted
From: Florian Westphal <fw@strlen.de> [ Upstream commit f07157792c633b528de5fc1dbe2e4ea54f8e09d4 ] mptcp_add_pending_subflow() performs a sock_hold() on the subflow, then adds the subflow to the join list. Without a sock_put the subflow sk won't be freed in case connect() fails. unreferenced object 0xffff88810c03b100 (size 3000): [..] sk_prot_alloc.isra.0+0x2f/0x110 sk_alloc+0x5d/0xc20 inet6_create+0x2b7/0xd30 __sock_create+0x17f/0x410 mptcp_subflow_create_socket+0xff/0x9c0 __mptcp_subflow_connect+0x1da/0xaf0 mptcp_pm_nl_work+0x6e0/0x1120 mptcp_worker+0x508/0x9a0 Fixes: 5b950ff4331ddda ("mptcp: link MPC subflow into msk only after accept")I don't see this change in 5.10, so why is this fix queued up?quoted
I have reported the following warnings and kernel crash on 5.10.26-rc2 [1] The bisect reported that issue pointing out to this commit. commit 460916534896e6d4f80a37152e0948db33376873 mptcp: put subflow sock on connect error This problem is specific to 5.10.26-rc2. Warning: -------- [ 1040.114695] refcount_t: addition on 0; use-after-free. [ 1040.119857] WARNING: CPU: 3 PID: 31925 at /usr/src/kernel/lib/refcount.c:25 refcount_warn_saturate+0xd7/0x100 [ 1040.129769] Modules linked in: act_mirred cls_u32 sch_netem sch_etf ip6table_nat xt_nat iptable_nat nf_nat ip6table_filter xt_conntrack nf_conntrack nf_defrag_ipv4 libcrc32c ip6_tables nf_defrag_ipv6 sch_fq iptable_filter xt_mark ip_tables cls_bpf sch_ingress algif_hash x86_pkg_temp_thermal fuse [last unloaded: test_blackhole_dev] [ 1040.159030] CPU: 3 PID: 31925 Comm: mptcp_connect Tainted: G W K 5.10.26-rc2 #1 [ 1040.167459] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS 2.2 05/23/2018 [ 1040.174851] RIP: 0010:refcount_warn_saturate+0xd7/0x100 And Kernel Panic: ------------- [ 1069.557485] BUG: kernel NULL pointer dereference, address: 0000000000000010 [ 1069.564446] #PF: supervisor read access in kernel mode [ 1069.569583] #PF: error_code(0x0000) - not-present page [ 1069.574714] PGD 0 P4D 0 [ 1069.577246] Oops: 0000 [#1] SMP PTIquoted
index 16adba172fb9..591546d0953f 100644--- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c@@ -1133,6 +1133,7 @@ int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc, spin_lock_bh(&msk->join_list_lock); list_add_tail(&subflow->node, &msk->join_list); spin_unlock_bh(&msk->join_list_lock); + sock_put(mptcp_subflow_tcp_sock(subflow)); return err;Crash is not surprising, the backport puts the socket in the 'success' path (list_add_tail). I don't see why this is in -stable, the faulty commit is not there? The upstream patch is: list_del(&subflow->node); spin_unlock_bh(&msk->join_list_lock); + sock_put(mptcp_subflow_tcp_sock(subflow)); [ Note the 'list_del', this is in the error unwind path ]Odd, I think something went wrong with Sasha's scripts.
I brought in the commit it depends on as a dependency for something else, but ended up throwing it away, forgetting about this commit. Sorry :( -- Thanks, Sasha