From: Ido Schimmel idosch@nvidia.com
[ Upstream commit f6205f8215f12a96518ac9469ff76294ae7bd612 ]
The 'used' and 'updated' fields in the FDB entry structure can be accessed concurrently by multiple threads, leading to reports such as [1]. Can be reproduced using [2].
Suppress these reports by annotating these accesses using READ_ONCE() / WRITE_ONCE().
[1] BUG: KCSAN: data-race in vxlan_xmit / vxlan_xmit
write to 0xffff942604d263a8 of 8 bytes by task 286 on cpu 0: vxlan_xmit+0xb29/0x2380 dev_hard_start_xmit+0x84/0x2f0 __dev_queue_xmit+0x45a/0x1650 packet_xmit+0x100/0x150 packet_sendmsg+0x2114/0x2ac0 __sys_sendto+0x318/0x330 __x64_sys_sendto+0x76/0x90 x64_sys_call+0x14e8/0x1c00 do_syscall_64+0x9e/0x1a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f
read to 0xffff942604d263a8 of 8 bytes by task 287 on cpu 2: vxlan_xmit+0xadf/0x2380 dev_hard_start_xmit+0x84/0x2f0 __dev_queue_xmit+0x45a/0x1650 packet_xmit+0x100/0x150 packet_sendmsg+0x2114/0x2ac0 __sys_sendto+0x318/0x330 __x64_sys_sendto+0x76/0x90 x64_sys_call+0x14e8/0x1c00 do_syscall_64+0x9e/0x1a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f
value changed: 0x00000000fffbac6e -> 0x00000000fffbac6f
Reported by Kernel Concurrency Sanitizer on: CPU: 2 UID: 0 PID: 287 Comm: mausezahn Not tainted 6.13.0-rc7-01544-gb4b270f11a02 #5 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014
[2] #!/bin/bash
set +H echo whitelist > /sys/kernel/debug/kcsan echo !vxlan_xmit > /sys/kernel/debug/kcsan
ip link add name vx0 up type vxlan id 10010 dstport 4789 local 192.0.2.1 bridge fdb add 00:11:22:33:44:55 dev vx0 self static dst 198.51.100.1 taskset -c 0 mausezahn vx0 -a own -b 00:11:22:33:44:55 -c 0 -q & taskset -c 2 mausezahn vx0 -a own -b 00:11:22:33:44:55 -c 0 -q &
Reviewed-by: Petr Machata petrm@nvidia.com Signed-off-by: Ido Schimmel idosch@nvidia.com Reviewed-by: Eric Dumazet edumazet@google.com Reviewed-by: Nikolay Aleksandrov razor@blackwall.org Link: https://patch.msgid.link/20250204145549.1216254-2-idosch@nvidia.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/vxlan.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c index ce11fb2b05561..7105ac37f341e 100644 --- a/drivers/net/vxlan.c +++ b/drivers/net/vxlan.c @@ -302,9 +302,9 @@ static int vxlan_fdb_info(struct sk_buff *skb, struct vxlan_dev *vxlan, nla_put_u32(skb, NDA_IFINDEX, rdst->remote_ifindex)) goto nla_put_failure;
- ci.ndm_used = jiffies_to_clock_t(now - fdb->used); + ci.ndm_used = jiffies_to_clock_t(now - READ_ONCE(fdb->used)); ci.ndm_confirmed = 0; - ci.ndm_updated = jiffies_to_clock_t(now - fdb->updated); + ci.ndm_updated = jiffies_to_clock_t(now - READ_ONCE(fdb->updated)); ci.ndm_refcnt = 0;
if (nla_put(skb, NDA_CACHEINFO, sizeof(ci), &ci)) @@ -510,8 +510,8 @@ static struct vxlan_fdb *vxlan_find_mac(struct vxlan_dev *vxlan, struct vxlan_fdb *f;
f = __vxlan_find_mac(vxlan, mac, vni); - if (f && f->used != jiffies) - f->used = jiffies; + if (f && READ_ONCE(f->used) != jiffies) + WRITE_ONCE(f->used, jiffies);
return f; } @@ -942,12 +942,12 @@ static int vxlan_fdb_update_existing(struct vxlan_dev *vxlan, !(f->flags & NTF_VXLAN_ADDED_BY_USER)) { if (f->state != state) { f->state = state; - f->updated = jiffies; + WRITE_ONCE(f->updated, jiffies); notify = 1; } if (f->flags != fdb_flags) { f->flags = fdb_flags; - f->updated = jiffies; + WRITE_ONCE(f->updated, jiffies); notify = 1; } } @@ -974,7 +974,7 @@ static int vxlan_fdb_update_existing(struct vxlan_dev *vxlan, }
if (ndm_flags & NTF_USE) - f->used = jiffies; + WRITE_ONCE(f->used, jiffies);
if (notify) { if (rd == NULL) @@ -1351,7 +1351,7 @@ static bool vxlan_snoop(struct net_device *dev, src_mac, &rdst->remote_ip.sa, &src_ip->sa);
rdst->remote_ip = *src_ip; - f->updated = jiffies; + WRITE_ONCE(f->updated, jiffies); vxlan_fdb_notify(vxlan, f, rdst, RTM_NEWNEIGH, true, NULL); } else { u32 hash_index = fdb_head_index(vxlan, src_mac, vni); @@ -2748,7 +2748,7 @@ static void vxlan_cleanup(struct timer_list *t) if (f->flags & NTF_EXT_LEARNED) continue;
- timeout = f->used + vxlan->cfg.age_interval * HZ; + timeout = READ_ONCE(f->used) + vxlan->cfg.age_interval * HZ; if (time_before_eq(timeout, jiffies)) { netdev_dbg(vxlan->dev, "garbage collect %pM\n",