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Subject[PATCH 4.19 13/96] ipv4: ensure rcu_read_lock() in ipv4_link_failure()
From: Eric Dumazet <>

[ Upstream commit c543cb4a5f07e09237ec0fc2c60c9f131b2c79ad ]

fib_compute_spec_dst() needs to be called under rcu protection.

syzbot reported :

WARNING: suspicious RCU usage
5.1.0-rc4+ #165 Not tainted
include/linux/inetdevice.h:220 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
1 lock held by swapper/0/0:
#0: 0000000051b67925 ((&n->timer)){+.-.}, at: lockdep_copy_map include/linux/lockdep.h:170 [inline]
#0: 0000000051b67925 ((&n->timer)){+.-.}, at: call_timer_fn+0xda/0x720 kernel/time/timer.c:1315

stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.1.0-rc4+ #165
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
lockdep_rcu_suspicious+0x153/0x15d kernel/locking/lockdep.c:5162
__in_dev_get_rcu include/linux/inetdevice.h:220 [inline]
fib_compute_spec_dst+0xbbd/0x1030 net/ipv4/fib_frontend.c:294
spec_dst_fill net/ipv4/ip_options.c:245 [inline]
__ip_options_compile+0x15a7/0x1a10 net/ipv4/ip_options.c:343
ipv4_link_failure+0x172/0x400 net/ipv4/route.c:1195
dst_link_failure include/net/dst.h:427 [inline]
arp_error_report+0xd1/0x1c0 net/ipv4/arp.c:297
neigh_invalidate+0x24b/0x570 net/core/neighbour.c:995
neigh_timer_handler+0xc35/0xf30 net/core/neighbour.c:1081
call_timer_fn+0x190/0x720 kernel/time/timer.c:1325
expire_timers kernel/time/timer.c:1362 [inline]
__run_timers kernel/time/timer.c:1681 [inline]
__run_timers kernel/time/timer.c:1649 [inline]
run_timer_softirq+0x652/0x1700 kernel/time/timer.c:1694
__do_softirq+0x266/0x95a kernel/softirq.c:293
invoke_softirq kernel/softirq.c:374 [inline]
irq_exit+0x180/0x1d0 kernel/softirq.c:414
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x14a/0x570 arch/x86/kernel/apic/apic.c:1062
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807

Fixes: ed0de45a1008 ("ipv4: recompile ip options in ipv4_link_failure")
Signed-off-by: Eric Dumazet <>
Reported-by: syzbot <>
Cc: Stephen Suryaputra <>
Signed-off-by: David S. Miller <>
Signed-off-by: Greg Kroah-Hartman <>
net/ipv4/route.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1187,14 +1187,20 @@ static struct dst_entry *ipv4_dst_check(

static void ipv4_link_failure(struct sk_buff *skb)
- struct rtable *rt;
struct ip_options opt;
+ struct rtable *rt;
+ int res;

/* Recompile ip options since IPCB may not be valid anymore.
memset(&opt, 0, sizeof(opt));
opt.optlen = ip_hdr(skb)->ihl*4 - sizeof(struct iphdr);
- if (__ip_options_compile(dev_net(skb->dev), &opt, skb, NULL))
+ rcu_read_lock();
+ res = __ip_options_compile(dev_net(skb->dev), &opt, skb, NULL);
+ rcu_read_unlock();
+ if (res)

__icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, 0, &opt);

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