neighbour: Fix __randomize_layout crash in struct neighbour

[ Upstream commit 45b3fae4675dc1d4ee2d7aefa19d85ee4f891377 ]

Previously, one-element and zero-length arrays were treated as true
flexible

neighbour: Fix __randomize_layout crash in struct neighbour

[ Upstream commit 45b3fae4675dc1d4ee2d7aefa19d85ee4f891377 ]

Previously, one-element and zero-length arrays were treated as true
flexible arrays, even though they are actually "fake" flex arrays.
The __randomize_layout would leave them untouched at the end of the
struct, similarly to proper C99 flex-array members.

However, this approach changed with commit 1ee60356c2dc ("gcc-plugins:
randstruct: Only warn about true flexible arrays"). Now, only C99
flexible-array members will remain untouched at the end of the struct,
while one-element and zero-length arrays will be subject to randomization.

Fix a `__randomize_layout` crash in `struct neighbour` by transforming
zero-length array `primary_key` into a proper C99 flexible-array member.

Fixes: 1ee60356c2dc ("gcc-plugins: randstruct: Only warn about true flexible arrays")
Closes: https://lore.kernel.org/linux-hardening/20231124102458.GB1503258@e124191.cambridge.arm.com/
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Joey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/r/ZWJoRsJGnCPdJ3+2@work
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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neighbour: fix data-races around n->output

n->output field can be read locklessly, while a writer
might change the pointer concurrently.

Add missing annotations to prevent load-store tearing.

Fixe

neighbour: fix data-races around n->output

n->output field can be read locklessly, while a writer
might change the pointer concurrently.

Add missing annotations to prevent load-store tearing.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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neighbour: Remove unused function declaration pneigh_for_each()

pneigh_for_each() is never implemented since the beginning of git history.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewe

neighbour: Remove unused function declaration pneigh_for_each()

pneigh_for_each() is never implemented since the beginning of git history.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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neighbour: fix unaligned access to pneigh_entry

After the blamed commit, the member key is longer 4-byte aligned. On
platforms that do not support unaligned access, e.g., MIPS32R2 with
unaligned_act

neighbour: fix unaligned access to pneigh_entry

After the blamed commit, the member key is longer 4-byte aligned. On
platforms that do not support unaligned access, e.g., MIPS32R2 with
unaligned_action set to 1, this will trigger a crash when accessing
an IPv6 pneigh_entry, as the key is cast to an in6_addr pointer.

Change the type of the key to u32 to make it aligned.

Fixes: 62dd93181aaa ("[IPV6] NDISC: Set per-entry is_router flag in Proxy NA.")
Signed-off-by: Qingfang DENG <qingfang.deng@siflower.com.cn>
Link: https://lore.kernel.org/r/20230601015432.159066-1-dqfext@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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neighbour: switch to standard rcu, instead of rcu_bh

rcu_bh is no longer a win, especially for objects freed
with standard call_rcu().

Switch neighbour code to no longer disable BH when not necessa

neighbour: switch to standard rcu, instead of rcu_bh

rcu_bh is no longer a win, especially for objects freed
with standard call_rcu().

Switch neighbour code to no longer disable BH when not necessary.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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neighbour: annotate lockless accesses to n->nud_state

We have many lockless accesses to n->nud_state.

Before adding another one in the following patch,
add annotations to readers and writers.

Sign

neighbour: annotate lockless accesses to n->nud_state

We have many lockless accesses to n->nud_state.

Before adding another one in the following patch,
add annotations to readers and writers.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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neighbour: delete neigh_lookup_nodev as not used

neigh_lookup_nodev isn't used in the kernel after removal
of DECnet. So let's remove it.

Fixes: 1202cdd66531 ("Remove DECnet support from kernel")
S

neighbour: delete neigh_lookup_nodev as not used

neigh_lookup_nodev isn't used in the kernel after removal
of DECnet. So let's remove it.

Fixes: 1202cdd66531 ("Remove DECnet support from kernel")
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://lore.kernel.org/r/eb5656200d7964b2d177a36b77efa3c597d6d72d.1678267343.git.leonro@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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net: neigh: decrement the family specific qlen

Commit 0ff4eb3d5ebb ("neighbour: make proxy_queue.qlen limit
per-device") introduced the length counter qlen in struct neigh_parms.
There are separate

net: neigh: decrement the family specific qlen

Commit 0ff4eb3d5ebb ("neighbour: make proxy_queue.qlen limit
per-device") introduced the length counter qlen in struct neigh_parms.
There are separate neigh_parms instances for IPv4/ARP and IPv6/ND, and
while the family specific qlen is incremented in pneigh_enqueue(), the
mentioned commit decrements always the IPv4/ARP specific qlen,
regardless of the currently processed family, in pneigh_queue_purge()
and neigh_proxy_process().

As a result, with IPv6/ND, the family specific qlen is only incremented
(and never decremented) until it exceeds PROXY_QLEN, and then, according
to the check in pneigh_enqueue(), neighbor solicitations are not
answered anymore. As an example, this is noted when using the
subnet-router anycast address to access a Linux router. After a certain
amount of time (in the observed case, qlen exceeded PROXY_QLEN after two
days), the Linux router stops answering neighbor solicitations for its
subnet-router anycast address and effectively becomes unreachable.

Another result with IPv6/ND is that the IPv4/ARP specific qlen is
decremented more often than incremented. This leads to negative qlen
values, as a signed integer has been used for the length counter qlen,
and potentially to an integer overflow.

Fix this by introducing the helper function neigh_parms_qlen_dec(),
which decrements the family specific qlen. Thereby, make use of the
existing helper function neigh_get_dev_parms_rcu(), whose definition
therefore needs to be placed earlier in neighbour.c. Take the family
member from struct neigh_table to determine the currently processed
family and appropriately call neigh_parms_qlen_dec() from
pneigh_queue_purge() and neigh_proxy_process().

Additionally, use an unsigned integer for the length counter qlen.

Fixes: 0ff4eb3d5ebb ("neighbour: make proxy_queue.qlen limit per-device")
Signed-off-by: Thomas Zeitlhofer <thomas.zeitlhofer+lkml@ze-it.at>
Signed-off-by: David S. Miller <davem@davemloft.net>

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neighbour: Remove unused inline function neigh_key_eq16()

All uses of neigh_key_eq16() have
been removed since commit 1202cdd66531 ("Remove DECnet support
from kernel"), so remove it.

Signed-off-by

neighbour: Remove unused inline function neigh_key_eq16()

All uses of neigh_key_eq16() have
been removed since commit 1202cdd66531 ("Remove DECnet support
from kernel"), so remove it.

Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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neighbour: make proxy_queue.qlen limit per-device

Right now we have a neigh_param PROXY_QLEN which specifies maximum length
of neigh_table->proxy_queue. But in fact, this limitation doesn't work wel

neighbour: make proxy_queue.qlen limit per-device

Right now we have a neigh_param PROXY_QLEN which specifies maximum length
of neigh_table->proxy_queue. But in fact, this limitation doesn't work well
because check condition looks like:
tbl->proxy_queue.qlen > NEIGH_VAR(p, PROXY_QLEN)

The problem is that p (struct neigh_parms) is a per-device thing,
but tbl (struct neigh_table) is a system-wide global thing.

It seems reasonable to make proxy_queue limit per-device based.

v2:
- nothing changed in this patch
v3:
- rebase to net tree

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@kernel.org>
Cc: Yajun Deng <yajun.deng@linux.dev>
Cc: Roopa Prabhu <roopa@nvidia.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com>
Cc: Konstantin Khorenko <khorenko@virtuozzo.com>
Cc: kernel@openvz.org
Cc: devel@openvz.org
Suggested-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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net, neigh: introduce interval_probe_time_ms for periodic probe

commit ed6cd6a17896 ("net, neigh: Set lower cap for neigh_managed_work rearming")
fixed a case when DELAY_PROBE_TIME is configured to

net, neigh: introduce interval_probe_time_ms for periodic probe

commit ed6cd6a17896 ("net, neigh: Set lower cap for neigh_managed_work rearming")
fixed a case when DELAY_PROBE_TIME is configured to 0, the processing of the
system work queue hog CPU to 100%, and further more we should introduce
a new option used by periodic probe

Signed-off-by: Yuwei Wang <wangyuweihx@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

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net, neigh: Do not trigger immediate probes on NUD_FAILED from neigh_managed_work

syzkaller was able to trigger a deadlock for NTF_MANAGED entries [0]:

kworker/0:16/14617 is trying to acquire loc

net, neigh: Do not trigger immediate probes on NUD_FAILED from neigh_managed_work

syzkaller was able to trigger a deadlock for NTF_MANAGED entries [0]:

kworker/0:16/14617 is trying to acquire lock:
ffffffff8d4dd370 (&tbl->lock){++-.}-{2:2}, at: ___neigh_create+0x9e1/0x2990 net/core/neighbour.c:652
[...]
but task is already holding lock:
ffffffff8d4dd370 (&tbl->lock){++-.}-{2:2}, at: neigh_managed_work+0x35/0x250 net/core/neighbour.c:1572

The neighbor entry turned to NUD_FAILED state, where __neigh_event_send()
triggered an immediate probe as per commit cd28ca0a3dd1 ("neigh: reduce
arp latency") via neigh_probe() given table lock was held.

One option to fix this situation is to defer the neigh_probe() back to
the neigh_timer_handler() similarly as pre cd28ca0a3dd1. For the case
of NTF_MANAGED, this deferral is acceptable given this only happens on
actual failure state and regular / expected state is NUD_VALID with the
entry already present.

The fix adds a parameter to __neigh_event_send() in order to communicate
whether immediate probe is allowed or disallowed. Existing call-sites
of neigh_event_send() default as-is to immediate probe. However, the
neigh_managed_work() disables it via use of neigh_event_send_probe().

[0] <TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_deadlock_bug kernel/locking/lockdep.c:2956 [inline]
check_deadlock kernel/locking/lockdep.c:2999 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire.cold+0x149/0x3ab kernel/locking/lockdep.c:5027
lock_acquire kernel/locking/lockdep.c:5639 [inline]
lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5604
__raw_write_lock_bh include/linux/rwlock_api_smp.h:202 [inline]
_raw_write_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:334
___neigh_create+0x9e1/0x2990 net/core/neighbour.c:652
ip6_finish_output2+0x1070/0x14f0 net/ipv6/ip6_output.c:123
__ip6_finish_output net/ipv6/ip6_output.c:191 [inline]
__ip6_finish_output+0x61e/0xe90 net/ipv6/ip6_output.c:170
ip6_finish_output+0x32/0x200 net/ipv6/ip6_output.c:201
NF_HOOK_COND include/linux/netfilter.h:296 [inline]
ip6_output+0x1e4/0x530 net/ipv6/ip6_output.c:224
dst_output include/net/dst.h:451 [inline]
NF_HOOK include/linux/netfilter.h:307 [inline]
ndisc_send_skb+0xa99/0x17f0 net/ipv6/ndisc.c:508
ndisc_send_ns+0x3a9/0x840 net/ipv6/ndisc.c:650
ndisc_solicit+0x2cd/0x4f0 net/ipv6/ndisc.c:742
neigh_probe+0xc2/0x110 net/core/neighbour.c:1040
__neigh_event_send+0x37d/0x1570 net/core/neighbour.c:1201
neigh_event_send include/net/neighbour.h:470 [inline]
neigh_managed_work+0x162/0x250 net/core/neighbour.c:1574
process_one_work+0x9ac/0x1650 kernel/workqueue.c:2307
worker_thread+0x657/0x1110 kernel/workqueue.c:2454
kthread+0x2e9/0x3a0 kernel/kthread.c:377
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>

Fixes: 7482e3841d52 ("net, neigh: Add NTF_MANAGED flag for managed neighbor entries")
Reported-by: syzbot+5239d0e1778a500d477a@syzkaller.appspotmail.com
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Roopa Prabhu <roopa@nvidia.com>
Tested-by: syzbot+5239d0e1778a500d477a@syzkaller.appspotmail.com
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20220201193942.5055-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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net: add net device refcount tracker to struct neigh_parms

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net: add net device refcount tracker to struct pneigh_entry

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net: add net device refcount tracker to struct neighbour

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

neigh: introduce neigh_confirm() helper function

Add neigh_confirm() for the confirmed member in struct neighbour,
it can be called as an independent unit by other functions.

Signed-off-by: Yajun D

neigh: introduce neigh_confirm() helper function

Add neigh_confirm() for the confirmed member in struct neighbour,
it can be called as an independent unit by other functions.

Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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net: annotate data-race in neigh_output()

neigh_output() reads n->nud_state and hh->hh_len locklessly.

This is fine, but we need to add annotations and document this.

We evaluate skip_cache first

net: annotate data-race in neigh_output()

neigh_output() reads n->nud_state and hh->hh_len locklessly.

This is fine, but we need to add annotations and document this.

We evaluate skip_cache first to avoid reading these fields
if the cache has to by bypassed.

syzbot report:

BUG: KCSAN: data-race in __neigh_event_send / ip_finish_output2

write to 0xffff88810798a885 of 1 bytes by interrupt on cpu 1:
__neigh_event_send+0x40d/0xac0 net/core/neighbour.c:1128
neigh_event_send include/net/neighbour.h:444 [inline]
neigh_resolve_output+0x104/0x410 net/core/neighbour.c:1476
neigh_output include/net/neighbour.h:510 [inline]
ip_finish_output2+0x80a/0xaa0 net/ipv4/ip_output.c:221
ip_finish_output+0x3b5/0x510 net/ipv4/ip_output.c:309
NF_HOOK_COND include/linux/netfilter.h:296 [inline]
ip_output+0xf3/0x1a0 net/ipv4/ip_output.c:423
dst_output include/net/dst.h:450 [inline]
ip_local_out+0x164/0x220 net/ipv4/ip_output.c:126
__ip_queue_xmit+0x9d3/0xa20 net/ipv4/ip_output.c:525
ip_queue_xmit+0x34/0x40 net/ipv4/ip_output.c:539
__tcp_transmit_skb+0x142a/0x1a00 net/ipv4/tcp_output.c:1405
tcp_transmit_skb net/ipv4/tcp_output.c:1423 [inline]
tcp_xmit_probe_skb net/ipv4/tcp_output.c:4011 [inline]
tcp_write_wakeup+0x4a9/0x810 net/ipv4/tcp_output.c:4064
tcp_send_probe0+0x2c/0x2b0 net/ipv4/tcp_output.c:4079
tcp_probe_timer net/ipv4/tcp_timer.c:398 [inline]
tcp_write_timer_handler+0x394/0x520 net/ipv4/tcp_timer.c:626
tcp_write_timer+0xb9/0x180 net/ipv4/tcp_timer.c:642
call_timer_fn+0x2e/0x1d0 kernel/time/timer.c:1421
expire_timers+0x135/0x240 kernel/time/timer.c:1466
__run_timers+0x368/0x430 kernel/time/timer.c:1734
run_timer_softirq+0x19/0x30 kernel/time/timer.c:1747
__do_softirq+0x12c/0x26e kernel/softirq.c:558
invoke_softirq kernel/softirq.c:432 [inline]
__irq_exit_rcu kernel/softirq.c:636 [inline]
irq_exit_rcu+0x4e/0xa0 kernel/softirq.c:648
sysvec_apic_timer_interrupt+0x69/0x80 arch/x86/kernel/apic/apic.c:1097
asm_sysvec_apic_timer_interrupt+0x12/0x20
native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
acpi_safe_halt drivers/acpi/processor_idle.c:109 [inline]
acpi_idle_do_entry drivers/acpi/processor_idle.c:553 [inline]
acpi_idle_enter+0x258/0x2e0 drivers/acpi/processor_idle.c:688
cpuidle_enter_state+0x2b4/0x760 drivers/cpuidle/cpuidle.c:237
cpuidle_enter+0x3c/0x60 drivers/cpuidle/cpuidle.c:351
call_cpuidle kernel/sched/idle.c:158 [inline]
cpuidle_idle_call kernel/sched/idle.c:239 [inline]
do_idle+0x1a3/0x250 kernel/sched/idle.c:306
cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:403
secondary_startup_64_no_verify+0xb1/0xbb

read to 0xffff88810798a885 of 1 bytes by interrupt on cpu 0:
neigh_output include/net/neighbour.h:507 [inline]
ip_finish_output2+0x79a/0xaa0 net/ipv4/ip_output.c:221
ip_finish_output+0x3b5/0x510 net/ipv4/ip_output.c:309
NF_HOOK_COND include/linux/netfilter.h:296 [inline]
ip_output+0xf3/0x1a0 net/ipv4/ip_output.c:423
dst_output include/net/dst.h:450 [inline]
ip_local_out+0x164/0x220 net/ipv4/ip_output.c:126
__ip_queue_xmit+0x9d3/0xa20 net/ipv4/ip_output.c:525
ip_queue_xmit+0x34/0x40 net/ipv4/ip_output.c:539
__tcp_transmit_skb+0x142a/0x1a00 net/ipv4/tcp_output.c:1405
tcp_transmit_skb net/ipv4/tcp_output.c:1423 [inline]
tcp_xmit_probe_skb net/ipv4/tcp_output.c:4011 [inline]
tcp_write_wakeup+0x4a9/0x810 net/ipv4/tcp_output.c:4064
tcp_send_probe0+0x2c/0x2b0 net/ipv4/tcp_output.c:4079
tcp_probe_timer net/ipv4/tcp_timer.c:398 [inline]
tcp_write_timer_handler+0x394/0x520 net/ipv4/tcp_timer.c:626
tcp_write_timer+0xb9/0x180 net/ipv4/tcp_timer.c:642
call_timer_fn+0x2e/0x1d0 kernel/time/timer.c:1421
expire_timers+0x135/0x240 kernel/time/timer.c:1466
__run_timers+0x368/0x430 kernel/time/timer.c:1734
run_timer_softirq+0x19/0x30 kernel/time/timer.c:1747
__do_softirq+0x12c/0x26e kernel/softirq.c:558
invoke_softirq kernel/softirq.c:432 [inline]
__irq_exit_rcu kernel/softirq.c:636 [inline]
irq_exit_rcu+0x4e/0xa0 kernel/softirq.c:648
sysvec_apic_timer_interrupt+0x69/0x80 arch/x86/kernel/apic/apic.c:1097
asm_sysvec_apic_timer_interrupt+0x12/0x20
native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
acpi_safe_halt drivers/acpi/processor_idle.c:109 [inline]
acpi_idle_do_entry drivers/acpi/processor_idle.c:553 [inline]
acpi_idle_enter+0x258/0x2e0 drivers/acpi/processor_idle.c:688
cpuidle_enter_state+0x2b4/0x760 drivers/cpuidle/cpuidle.c:237
cpuidle_enter+0x3c/0x60 drivers/cpuidle/cpuidle.c:351
call_cpuidle kernel/sched/idle.c:158 [inline]
cpuidle_idle_call kernel/sched/idle.c:239 [inline]
do_idle+0x1a3/0x250 kernel/sched/idle.c:306
cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:403
rest_init+0xee/0x100 init/main.c:734
arch_call_rest_init+0xa/0xb
start_kernel+0x5e4/0x669 init/main.c:1142
secondary_startup_64_no_verify+0xb1/0xbb

value changed: 0x20 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.15.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

net, neigh: Add NTF_MANAGED flag for managed neighbor entries

Allow a user space control plane to insert entries with a new NTF_EXT_MANAGED
flag. The flag then indicates to the kernel that the neigh

net, neigh: Add NTF_MANAGED flag for managed neighbor entries

Allow a user space control plane to insert entries with a new NTF_EXT_MANAGED
flag. The flag then indicates to the kernel that the neighbor entry should be
periodically probed for keeping the entry in NUD_REACHABLE state iff possible.

The use case for this is targeting XDP or tc BPF load-balancers which use
the bpf_fib_lookup() BPF helper in order to piggyback on neighbor resolution
for their backends. Given they cannot be resolved in fast-path, a control
plane inserts the L3 (without L2) entries manually into the neighbor table
and lets the kernel do the neighbor resolution either on the gateway or on
the backend directly in case the latter resides in the same L2. This avoids
to deal with L2 in the control plane and to rebuild what the kernel already
does best anyway.

NTF_EXT_MANAGED can be combined with NTF_EXT_LEARNED in order to avoid GC
eviction. The kernel then adds NTF_MANAGED flagged entries to a per-neighbor
table which gets triggered by the system work queue to periodically call
neigh_event_send() for performing the resolution. The implementation allows
migration from/to NTF_MANAGED neighbor entries, so that already existing
entries can be converted by the control plane if needed. Potentially, we could
make the interval for periodically calling neigh_event_send() configurable;
right now it's set to DELAY_PROBE_TIME which is also in line with mlxsw which
has similar driver-internal infrastructure c723c735fa6b ("mlxsw: spectrum_router:
Periodically update the kernel's neigh table"). In future, the latter could
possibly reuse the NTF_MANAGED neighbors as well.

Example:

# ./ip/ip n replace 192.168.178.30 dev enp5s0 managed extern_learn
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a managed extern_learn REACHABLE
[...]

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Roopa Prabhu <roopa@nvidia.com>
Link: https://linuxplumbersconf.org/event/11/contributions/953/
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

net, neigh: Extend neigh->flags to 32 bit to allow for extensions

Currently, all bits in struct ndmsg's ndm_flags are used up with the most
recent addition of 435f2e7cc0b7 ("net: bridge: add support

net, neigh: Extend neigh->flags to 32 bit to allow for extensions

Currently, all bits in struct ndmsg's ndm_flags are used up with the most
recent addition of 435f2e7cc0b7 ("net: bridge: add support for sticky fdb
entries"). This makes it impossible to extend the neighboring subsystem
with new NTF_* flags:

struct ndmsg {
__u8 ndm_family;
__u8 ndm_pad1;
__u16 ndm_pad2;
__s32 ndm_ifindex;
__u16 ndm_state;
__u8 ndm_flags;
__u8 ndm_type;
};

There are ndm_pad{1,2} attributes which are not used. However, due to
uncareful design, the kernel does not enforce them to be zero upon new
neighbor entry addition, and given they've been around forever, it is
not possible to reuse them today due to risk of breakage. One option to
overcome this limitation is to add a new NDA_FLAGS_EXT attribute for
extended flags.

In struct neighbour, there is a 3 byte hole between protocol and ha_lock,
which allows neigh->flags to be extended from 8 to 32 bits while still
being on the same cacheline as before. This also allows for all future
NTF_* flags being in neigh->flags rather than yet another flags field.
Unknown flags in NDA_FLAGS_EXT will be rejected by the kernel.

Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Roopa Prabhu <roopa@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

net, neigh: Enable state migration between NUD_PERMANENT and NTF_USE

Currently, it is not possible to migrate a neighbor entry between NUD_PERMANENT
state and NTF_USE flag with a dynamic NUD state f

net, neigh: Enable state migration between NUD_PERMANENT and NTF_USE

Currently, it is not possible to migrate a neighbor entry between NUD_PERMANENT
state and NTF_USE flag with a dynamic NUD state from a user space control plane.
Similarly, it is not possible to add/remove NTF_EXT_LEARNED flag from an existing
neighbor entry in combination with NTF_USE flag.

This is due to the latter directly calling into neigh_event_send() without any
meta data updates as happening in __neigh_update(). Thus, to enable this use
case, extend the latter with a NEIGH_UPDATE_F_USE flag where we break the
NUD_PERMANENT state in particular so that a latter neigh_event_send() is able
to re-resolve a neighbor entry.

Before fix, NUD_PERMANENT -> NUD_* & NTF_USE:

# ./ip/ip n replace 192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a PERMANENT
[...]
# ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a PERMANENT
[...]

As can be seen, despite the admin-triggered replace, the entry remains in the
NUD_PERMANENT state.

After fix, NUD_PERMANENT -> NUD_* & NTF_USE:

# ./ip/ip n replace 192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a PERMANENT
[...]
# ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a extern_learn REACHABLE
[...]
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a extern_learn STALE
[...]
# ./ip/ip n replace 192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a PERMANENT
[...]

After the fix, the admin-triggered replace switches to a dynamic state from
the NTF_USE flag which triggered a new neighbor resolution. Likewise, we can
transition back from there, if needed, into NUD_PERMANENT.

Similar before/after behavior can be observed for below transitions:

Before fix, NTF_USE -> NTF_USE | NTF_EXT_LEARNED -> NTF_USE:

# ./ip/ip n replace 192.168.178.30 dev enp5s0 use
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a REACHABLE
[...]
# ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a REACHABLE
[...]

After fix, NTF_USE -> NTF_USE | NTF_EXT_LEARNED -> NTF_USE:

# ./ip/ip n replace 192.168.178.30 dev enp5s0 use
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a REACHABLE
[...]
# ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a extern_learn REACHABLE
[...]
# ./ip/ip n replace 192.168.178.30 dev enp5s0 use
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a REACHABLE
[..]

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Roopa Prabhu <roopa@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

net, neigh: Enable state migration between NUD_PERMANENT and NTF_USE

[ Upstream commit 3dc20f4762c62d3b3f0940644881ed818aa7b2f5 ]

Currently, it is not possible to migrate a neighbor entry between N

net, neigh: Enable state migration between NUD_PERMANENT and NTF_USE

[ Upstream commit 3dc20f4762c62d3b3f0940644881ed818aa7b2f5 ]

Currently, it is not possible to migrate a neighbor entry between NUD_PERMANENT
state and NTF_USE flag with a dynamic NUD state from a user space control plane.
Similarly, it is not possible to add/remove NTF_EXT_LEARNED flag from an existing
neighbor entry in combination with NTF_USE flag.

This is due to the latter directly calling into neigh_event_send() without any
meta data updates as happening in __neigh_update(). Thus, to enable this use
case, extend the latter with a NEIGH_UPDATE_F_USE flag where we break the
NUD_PERMANENT state in particular so that a latter neigh_event_send() is able
to re-resolve a neighbor entry.

Before fix, NUD_PERMANENT -> NUD_* & NTF_USE:

# ./ip/ip n replace 192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a PERMANENT
[...]
# ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a PERMANENT
[...]

As can be seen, despite the admin-triggered replace, the entry remains in the
NUD_PERMANENT state.

After fix, NUD_PERMANENT -> NUD_* & NTF_USE:

# ./ip/ip n replace 192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a PERMANENT
[...]
# ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a extern_learn REACHABLE
[...]
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a extern_learn STALE
[...]
# ./ip/ip n replace 192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a PERMANENT
[...]

After the fix, the admin-triggered replace switches to a dynamic state from
the NTF_USE flag which triggered a new neighbor resolution. Likewise, we can
transition back from there, if needed, into NUD_PERMANENT.

Similar before/after behavior can be observed for below transitions:

Before fix, NTF_USE -> NTF_USE | NTF_EXT_LEARNED -> NTF_USE:

# ./ip/ip n replace 192.168.178.30 dev enp5s0 use
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a REACHABLE
[...]
# ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a REACHABLE
[...]

After fix, NTF_USE -> NTF_USE | NTF_EXT_LEARNED -> NTF_USE:

# ./ip/ip n replace 192.168.178.30 dev enp5s0 use
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a REACHABLE
[...]
# ./ip/ip n replace 192.168.178.30 dev enp5s0 use extern_learn
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a extern_learn REACHABLE
[...]
# ./ip/ip n replace 192.168.178.30 dev enp5s0 use
# ./ip/ip n
192.168.178.30 dev enp5s0 lladdr f4:8c:50:5e:71:9a REACHABLE
[..]

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Roopa Prabhu <roopa@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

net: annotate data-race in neigh_output()

[ Upstream commit d18785e213866935b4c3dc0c33c3e18801ce0ce8 ]

neigh_output() reads n->nud_state and hh->hh_len locklessly.

This is fine, but we need to add

net: annotate data-race in neigh_output()

[ Upstream commit d18785e213866935b4c3dc0c33c3e18801ce0ce8 ]

neigh_output() reads n->nud_state and hh->hh_len locklessly.

This is fine, but we need to add annotations and document this.

We evaluate skip_cache first to avoid reading these fields
if the cache has to by bypassed.

syzbot report:

BUG: KCSAN: data-race in __neigh_event_send / ip_finish_output2

write to 0xffff88810798a885 of 1 bytes by interrupt on cpu 1:
__neigh_event_send+0x40d/0xac0 net/core/neighbour.c:1128
neigh_event_send include/net/neighbour.h:444 [inline]
neigh_resolve_output+0x104/0x410 net/core/neighbour.c:1476
neigh_output include/net/neighbour.h:510 [inline]
ip_finish_output2+0x80a/0xaa0 net/ipv4/ip_output.c:221
ip_finish_output+0x3b5/0x510 net/ipv4/ip_output.c:309
NF_HOOK_COND include/linux/netfilter.h:296 [inline]
ip_output+0xf3/0x1a0 net/ipv4/ip_output.c:423
dst_output include/net/dst.h:450 [inline]
ip_local_out+0x164/0x220 net/ipv4/ip_output.c:126
__ip_queue_xmit+0x9d3/0xa20 net/ipv4/ip_output.c:525
ip_queue_xmit+0x34/0x40 net/ipv4/ip_output.c:539
__tcp_transmit_skb+0x142a/0x1a00 net/ipv4/tcp_output.c:1405
tcp_transmit_skb net/ipv4/tcp_output.c:1423 [inline]
tcp_xmit_probe_skb net/ipv4/tcp_output.c:4011 [inline]
tcp_write_wakeup+0x4a9/0x810 net/ipv4/tcp_output.c:4064
tcp_send_probe0+0x2c/0x2b0 net/ipv4/tcp_output.c:4079
tcp_probe_timer net/ipv4/tcp_timer.c:398 [inline]
tcp_write_timer_handler+0x394/0x520 net/ipv4/tcp_timer.c:626
tcp_write_timer+0xb9/0x180 net/ipv4/tcp_timer.c:642
call_timer_fn+0x2e/0x1d0 kernel/time/timer.c:1421
expire_timers+0x135/0x240 kernel/time/timer.c:1466
__run_timers+0x368/0x430 kernel/time/timer.c:1734
run_timer_softirq+0x19/0x30 kernel/time/timer.c:1747
__do_softirq+0x12c/0x26e kernel/softirq.c:558
invoke_softirq kernel/softirq.c:432 [inline]
__irq_exit_rcu kernel/softirq.c:636 [inline]
irq_exit_rcu+0x4e/0xa0 kernel/softirq.c:648
sysvec_apic_timer_interrupt+0x69/0x80 arch/x86/kernel/apic/apic.c:1097
asm_sysvec_apic_timer_interrupt+0x12/0x20
native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
acpi_safe_halt drivers/acpi/processor_idle.c:109 [inline]
acpi_idle_do_entry drivers/acpi/processor_idle.c:553 [inline]
acpi_idle_enter+0x258/0x2e0 drivers/acpi/processor_idle.c:688
cpuidle_enter_state+0x2b4/0x760 drivers/cpuidle/cpuidle.c:237
cpuidle_enter+0x3c/0x60 drivers/cpuidle/cpuidle.c:351
call_cpuidle kernel/sched/idle.c:158 [inline]
cpuidle_idle_call kernel/sched/idle.c:239 [inline]
do_idle+0x1a3/0x250 kernel/sched/idle.c:306
cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:403
secondary_startup_64_no_verify+0xb1/0xbb

read to 0xffff88810798a885 of 1 bytes by interrupt on cpu 0:
neigh_output include/net/neighbour.h:507 [inline]
ip_finish_output2+0x79a/0xaa0 net/ipv4/ip_output.c:221
ip_finish_output+0x3b5/0x510 net/ipv4/ip_output.c:309
NF_HOOK_COND include/linux/netfilter.h:296 [inline]
ip_output+0xf3/0x1a0 net/ipv4/ip_output.c:423
dst_output include/net/dst.h:450 [inline]
ip_local_out+0x164/0x220 net/ipv4/ip_output.c:126
__ip_queue_xmit+0x9d3/0xa20 net/ipv4/ip_output.c:525
ip_queue_xmit+0x34/0x40 net/ipv4/ip_output.c:539
__tcp_transmit_skb+0x142a/0x1a00 net/ipv4/tcp_output.c:1405
tcp_transmit_skb net/ipv4/tcp_output.c:1423 [inline]
tcp_xmit_probe_skb net/ipv4/tcp_output.c:4011 [inline]
tcp_write_wakeup+0x4a9/0x810 net/ipv4/tcp_output.c:4064
tcp_send_probe0+0x2c/0x2b0 net/ipv4/tcp_output.c:4079
tcp_probe_timer net/ipv4/tcp_timer.c:398 [inline]
tcp_write_timer_handler+0x394/0x520 net/ipv4/tcp_timer.c:626
tcp_write_timer+0xb9/0x180 net/ipv4/tcp_timer.c:642
call_timer_fn+0x2e/0x1d0 kernel/time/timer.c:1421
expire_timers+0x135/0x240 kernel/time/timer.c:1466
__run_timers+0x368/0x430 kernel/time/timer.c:1734
run_timer_softirq+0x19/0x30 kernel/time/timer.c:1747
__do_softirq+0x12c/0x26e kernel/softirq.c:558
invoke_softirq kernel/softirq.c:432 [inline]
__irq_exit_rcu kernel/softirq.c:636 [inline]
irq_exit_rcu+0x4e/0xa0 kernel/softirq.c:648
sysvec_apic_timer_interrupt+0x69/0x80 arch/x86/kernel/apic/apic.c:1097
asm_sysvec_apic_timer_interrupt+0x12/0x20
native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
acpi_safe_halt drivers/acpi/processor_idle.c:109 [inline]
acpi_idle_do_entry drivers/acpi/processor_idle.c:553 [inline]
acpi_idle_enter+0x258/0x2e0 drivers/acpi/processor_idle.c:688
cpuidle_enter_state+0x2b4/0x760 drivers/cpuidle/cpuidle.c:237
cpuidle_enter+0x3c/0x60 drivers/cpuidle/cpuidle.c:351
call_cpuidle kernel/sched/idle.c:158 [inline]
cpuidle_idle_call kernel/sched/idle.c:239 [inline]
do_idle+0x1a3/0x250 kernel/sched/idle.c:306
cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:403
rest_init+0xee/0x100 init/main.c:734
arch_call_rest_init+0xa/0xb
start_kernel+0x5e4/0x669 init/main.c:1142
secondary_startup_64_no_verify+0xb1/0xbb

value changed: 0x20 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.15.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

net: Exempt multicast addresses from five-second neighbor lifetime

Commit 58956317c8de ("neighbor: Improve garbage collection")
guarantees neighbour table entries a five-second lifetime. Processes

net: Exempt multicast addresses from five-second neighbor lifetime

Commit 58956317c8de ("neighbor: Improve garbage collection")
guarantees neighbour table entries a five-second lifetime. Processes
which make heavy use of multicast can fill the neighour table with
multicast addresses in five seconds. At that point, neighbour entries
can't be GC-ed because they aren't five seconds old yet, the kernel
log starts to fill up with "neighbor table overflow!" messages, and
sends start to fail.

This patch allows multicast addresses to be thrown out before they've
lived out their five seconds. This makes room for non-multicast
addresses and makes messages to all addresses more reliable in these
circumstances.

Fixes: 58956317c8de ("neighbor: Improve garbage collection")
Signed-off-by: Jeff Dike <jdike@akamai.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20201113015815.31397-1-jdike@akamai.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

show more ...

net/sysctl: remove leftover __user annotations on neigh_proc_dointvec*

Remove the leftover __user annotation on the prototypes for
neigh_proc_dointvec*. The implementations already got this right,

net/sysctl: remove leftover __user annotations on neigh_proc_dointvec*

Remove the leftover __user annotation on the prototypes for
neigh_proc_dointvec*. The implementations already got this right, but
the headers kept the __user tags around.

Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler")
Reported-by: build test robot <lkp@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

show more ...

neighbour: Replace zero-length array with flexible-array member

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare

neighbour: Replace zero-length array with flexible-array member

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
int stuff;
struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...