6.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kuniyuki Iwashima kuniyu@google.com
[ Upstream commit 1bbb76a899486827394530916f01214d049931b3 ]
kernel test robot reported null-ptr-deref in neigh_flush_dev(). [0]
The cited commit introduced per-netdev neighbour list and converted neigh_flush_dev() to use it instead of the global hash table.
One thing we missed is that neigh_table_clear() calls neigh_ifdown() with NULL dev.
Let's restore the hash table iteration.
Note that IPv6 module is no longer unloadable, so neigh_table_clear() is called only when IPv6 fails to initialise, which is unlikely to happen.
[0]: IPv6: Attempt to unregister permanent protocol 136 IPv6: Attempt to unregister permanent protocol 17 Oops: general protection fault, probably for non-canonical address 0xdffffc00000001a0: 0000 [#1] SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000d00-0x0000000000000d07] CPU: 1 UID: 0 PID: 1 Comm: systemd Tainted: G T 6.12.0-rc6-01246-gf7f52738637f #1 Tainted: [T]=RANDSTRUCT Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 RIP: 0010:neigh_flush_dev.llvm.6395807810224103582+0x52/0x570 Code: c1 e8 03 42 8a 04 38 84 c0 0f 85 15 05 00 00 31 c0 41 83 3e 0a 0f 94 c0 48 8d 1c c3 48 81 c3 f8 0c 00 00 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 f7 49 93 fe 4c 8b 3b 4d 85 ff 0f RSP: 0000:ffff88810026f408 EFLAGS: 00010206 RAX: 00000000000001a0 RBX: 0000000000000d00 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffc0631640 RBP: ffff88810026f470 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: ffffffffc0625250 R14: ffffffffc0631640 R15: dffffc0000000000 FS: 00007f575cb83940(0000) GS:ffff8883aee00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f575db40008 CR3: 00000002bf936000 CR4: 00000000000406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> __neigh_ifdown.llvm.6395807810224103582+0x44/0x390 neigh_table_clear+0xb1/0x268 ndisc_cleanup+0x21/0x38 [ipv6] init_module+0x2f5/0x468 [ipv6] do_one_initcall+0x1ba/0x628 do_init_module+0x21a/0x530 load_module+0x2550/0x2ea0 __se_sys_finit_module+0x3d2/0x620 __x64_sys_finit_module+0x76/0x88 x64_sys_call+0x7ff/0xde8 do_syscall_64+0xfb/0x1e8 entry_SYSCALL_64_after_hwframe+0x67/0x6f RIP: 0033:0x7f575d6f2719 Code: 08 89 e8 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d b7 06 0d 00 f7 d8 64 89 01 48 RSP: 002b:00007fff82a2a268 EFLAGS: 00000246 ORIG_RAX: 0000000000000139 RAX: ffffffffffffffda RBX: 0000557827b45310 RCX: 00007f575d6f2719 RDX: 0000000000000000 RSI: 00007f575d584efd RDI: 0000000000000004 RBP: 00007f575d584efd R08: 0000000000000000 R09: 0000557827b47b00 R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000020000 R13: 0000000000000000 R14: 0000557827b470e0 R15: 00007f575dbb4270 </TASK> Modules linked in: ipv6(+)
Fixes: f7f52738637f4 ("neighbour: Create netdev->neighbour association") Reported-by: kernel test robot oliver.sang@intel.com Closes: https://lore.kernel.org/oe-lkp/202507200931.7a89ecd8-lkp@intel.com Signed-off-by: Kuniyuki Iwashima kuniyu@google.com Link: https://patch.msgid.link/20250723195443.448163-1-kuniyu@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/neighbour.c | 88 ++++++++++++++++++++++++++++++-------------- 1 file changed, 61 insertions(+), 27 deletions(-)
diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 49dce9a82295..a8dc72eda202 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -368,6 +368,43 @@ static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net, } }
+static void neigh_flush_one(struct neighbour *n) +{ + hlist_del_rcu(&n->hash); + hlist_del_rcu(&n->dev_list); + + write_lock(&n->lock); + + neigh_del_timer(n); + neigh_mark_dead(n); + + if (refcount_read(&n->refcnt) != 1) { + /* The most unpleasant situation. + * We must destroy neighbour entry, + * but someone still uses it. + * + * The destroy will be delayed until + * the last user releases us, but + * we must kill timers etc. and move + * it to safe state. + */ + __skb_queue_purge(&n->arp_queue); + n->arp_queue_len_bytes = 0; + WRITE_ONCE(n->output, neigh_blackhole); + + if (n->nud_state & NUD_VALID) + n->nud_state = NUD_NOARP; + else + n->nud_state = NUD_NONE; + + neigh_dbg(2, "neigh %p is stray\n", n); + } + + write_unlock(&n->lock); + + neigh_cleanup_and_release(n); +} + static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev, bool skip_perm) { @@ -381,32 +418,24 @@ static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev, if (skip_perm && n->nud_state & NUD_PERMANENT) continue;
- hlist_del_rcu(&n->hash); - hlist_del_rcu(&n->dev_list); - write_lock(&n->lock); - neigh_del_timer(n); - neigh_mark_dead(n); - if (refcount_read(&n->refcnt) != 1) { - /* The most unpleasant situation. - * We must destroy neighbour entry, - * but someone still uses it. - * - * The destroy will be delayed until - * the last user releases us, but - * we must kill timers etc. and move - * it to safe state. - */ - __skb_queue_purge(&n->arp_queue); - n->arp_queue_len_bytes = 0; - WRITE_ONCE(n->output, neigh_blackhole); - if (n->nud_state & NUD_VALID) - n->nud_state = NUD_NOARP; - else - n->nud_state = NUD_NONE; - neigh_dbg(2, "neigh %p is stray\n", n); - } - write_unlock(&n->lock); - neigh_cleanup_and_release(n); + neigh_flush_one(n); + } +} + +static void neigh_flush_table(struct neigh_table *tbl) +{ + struct neigh_hash_table *nht; + int i; + + nht = rcu_dereference_protected(tbl->nht, + lockdep_is_held(&tbl->lock)); + + for (i = 0; i < (1 << nht->hash_shift); i++) { + struct hlist_node *tmp; + struct neighbour *n; + + neigh_for_each_in_bucket_safe(n, tmp, &nht->hash_heads[i]) + neigh_flush_one(n); } }
@@ -422,7 +451,12 @@ static int __neigh_ifdown(struct neigh_table *tbl, struct net_device *dev, bool skip_perm) { write_lock_bh(&tbl->lock); - neigh_flush_dev(tbl, dev, skip_perm); + if (likely(dev)) { + neigh_flush_dev(tbl, dev, skip_perm); + } else { + DEBUG_NET_WARN_ON_ONCE(skip_perm); + neigh_flush_table(tbl); + } pneigh_ifdown_and_unlock(tbl, dev); pneigh_queue_purge(&tbl->proxy_queue, dev ? dev_net(dev) : NULL, tbl->family);