[pve-devel] applied: [PATCH kernel 4.13] fix #1737: merge: net: fix deadlock while clearing neighbor proxy table

Thomas Lamprecht t.lamprecht at proxmox.com
Wed Apr 25 15:22:15 CEST 2018


applied to respective branches.

On 4/25/18 8:23 AM, Wolfgang Bumiller wrote:
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=199289
> Signed-off-by: Wolfgang Bumiller <w.bumiller at proxmox.com>
> ---
> This has gone upstream by now.
> Difference between 4.13 and 4.15 is just the number in the filename ;-)
> 
>  ...dlock-while-clearing-neighbor-proxy-table.patch | 95 ++++++++++++++++++++++
>  1 file changed, 95 insertions(+)
>  create mode 100644 patches/kernel/0025-net-fix-deadlock-while-clearing-neighbor-proxy-table.patch
> 
> diff --git a/patches/kernel/0025-net-fix-deadlock-while-clearing-neighbor-proxy-table.patch b/patches/kernel/0025-net-fix-deadlock-while-clearing-neighbor-proxy-table.patch
> new file mode 100644
> index 0000000..a7e0ff2
> --- /dev/null
> +++ b/patches/kernel/0025-net-fix-deadlock-while-clearing-neighbor-proxy-table.patch
> @@ -0,0 +1,95 @@
> +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
> +From: Wolfgang Bumiller <w.bumiller at proxmox.com>
> +Date: Mon, 9 Apr 2018 14:56:29 +0200
> +Subject: [PATCH linux] net: fix deadlock while clearing neighbor proxy table
> +
> +When coming from ndisc_netdev_event() in net/ipv6/ndisc.c,
> +neigh_ifdown() is called with &nd_tbl, locking this while
> +clearing the proxy neighbor entries when eg. deleting an
> +interface. Calling the table's pndisc_destructor() with the
> +lock still held, however, can cause a deadlock: When a
> +multicast listener is available an IGMP packet of type
> +ICMPV6_MGM_REDUCTION may be sent out. When reaching
> +ip6_finish_output2(), if no neighbor entry for the target
> +address is found, __neigh_create() is called with &nd_tbl,
> +which it'll want to lock.
> +
> +Move the elements into their own list, then unlock the table
> +and perform the destruction.
> +
> +Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199289
> +Fixes: 6fd6ce2056de ("ipv6: Do not depend on rt->n in ip6_finish_output2().")
> +Signed-off-by: Wolfgang Bumiller <w.bumiller at proxmox.com>
> +---
> + net/core/neighbour.c | 28 ++++++++++++++++++----------
> + 1 file changed, 18 insertions(+), 10 deletions(-)
> +
> +diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> +index 7b7a14abba28..e22d2aefbd78 100644
> +--- a/net/core/neighbour.c
> ++++ b/net/core/neighbour.c
> +@@ -55,7 +55,8 @@ static void neigh_timer_handler(struct timer_list *t);
> + static void __neigh_notify(struct neighbour *n, int type, int flags,
> + 			   u32 pid);
> + static void neigh_update_notify(struct neighbour *neigh, u32 nlmsg_pid);
> +-static int pneigh_ifdown(struct neigh_table *tbl, struct net_device *dev);
> ++static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
> ++				    struct net_device *dev);
> + 
> + #ifdef CONFIG_PROC_FS
> + static const struct file_operations neigh_stat_seq_fops;
> +@@ -291,8 +292,7 @@ int neigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
> + {
> + 	write_lock_bh(&tbl->lock);
> + 	neigh_flush_dev(tbl, dev);
> +-	pneigh_ifdown(tbl, dev);
> +-	write_unlock_bh(&tbl->lock);
> ++	pneigh_ifdown_and_unlock(tbl, dev);
> + 
> + 	del_timer_sync(&tbl->proxy_timer);
> + 	pneigh_queue_purge(&tbl->proxy_queue);
> +@@ -681,9 +681,10 @@ int pneigh_delete(struct neigh_table *tbl, struct net *net, const void *pkey,
> + 	return -ENOENT;
> + }
> + 
> +-static int pneigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
> ++static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
> ++				    struct net_device *dev)
> + {
> +-	struct pneigh_entry *n, **np;
> ++	struct pneigh_entry *n, **np, *freelist = NULL;
> + 	u32 h;
> + 
> + 	for (h = 0; h <= PNEIGH_HASHMASK; h++) {
> +@@ -691,16 +692,23 @@ static int pneigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
> + 		while ((n = *np) != NULL) {
> + 			if (!dev || n->dev == dev) {
> + 				*np = n->next;
> +-				if (tbl->pdestructor)
> +-					tbl->pdestructor(n);
> +-				if (n->dev)
> +-					dev_put(n->dev);
> +-				kfree(n);
> ++				n->next = freelist;
> ++				freelist = n;
> + 				continue;
> + 			}
> + 			np = &n->next;
> + 		}
> + 	}
> ++	write_unlock_bh(&tbl->lock);
> ++	while ((n = freelist)) {
> ++		freelist = n->next;
> ++		n->next = NULL;
> ++		if (tbl->pdestructor)
> ++			tbl->pdestructor(n);
> ++		if (n->dev)
> ++			dev_put(n->dev);
> ++		kfree(n);
> ++	}
> + 	return -ENOENT;
> + }
> + 
> +-- 
> +2.11.0
> +
> 




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