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ipmr, ip6mr: annotate data-races in vif_seq_show()

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ipmr_vif_seq_show() and ip6mr_vif_seq_show() read vif->bytes_in,
vif->pkt_in, vif->bytes_out and vif->pkt_out with only rcu_read_lock()
held: since commit b96ef16d2f ("ipmr: convert /proc handlers to
rcu_read_lock()") both seq_start helpers are annotated __acquires(RCU)
and no longer take mrt_lock.

Those counters are updated from softirq context and the writers already
use WRITE_ONCE(): ipmr_prepare_xmit() and ip_mr_forward() on the IPv4
side, ip6mr_prepare_xmit() and ip6_mr_forward() on the IPv6 side. The
other lockless readers use READ_ONCE() as well - ipmr_ioctl(),
ipmr_compat_ioctl(), ipmr_fill_vif(), ip6mr_ioctl() and
ip6mr_compat_ioctl().

The two vif_seq_show() helpers are the only remaining bare readers, so
KCSAN flags them and the compiler is free to tear or reload the values
while the /proc/net/ip_mr_vif and /proc/net/ip6_mr_vif lines are being
formatted. Annotate them like the other readers; these are plain
statistics, no locking is needed.

Signed-off-by: Linkui Xiao <xiaolinkui@kylinos.cn>
Link: https://patch.msgid.link/20260910093452.2070079-1-xiaolinkui@126.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Linkui Xiao 2026-09-10 17:34:52 +08:00 committed by Jakub Kicinski
parent ad6ff1a67b
commit 0019aa65bb
2 changed files with 6 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
net/ipv4/ipmr.c
View File

@ -3178,8 +3178,9 @@ static int ipmr_vif_seq_show(struct seq_file *seq, void *v)
seq_printf(seq,
"%2td %-10s %8ld %7ld %8ld %7ld %05X %08X %08X\n",
vif - mrt->vif_table,
name, vif->bytes_in, vif->pkt_in,
vif->bytes_out, vif->pkt_out,
name,
READ_ONCE(vif->bytes_in), READ_ONCE(vif->pkt_in),
READ_ONCE(vif->bytes_out), READ_ONCE(vif->pkt_out),
vif->flags, vif->local, vif->remote);
}
return 0;

5
net/ipv6/ip6mr.c
View File

@ -485,8 +485,9 @@ static int ip6mr_vif_seq_show(struct seq_file *seq, void *v)
seq_printf(seq,
"%2td %-10s %8ld %7ld %8ld %7ld %05X\n",
vif - mrt->vif_table,
name, vif->bytes_in, vif->pkt_in,
vif->bytes_out, vif->pkt_out,
name,
READ_ONCE(vif->bytes_in), READ_ONCE(vif->pkt_in),
READ_ONCE(vif->bytes_out), READ_ONCE(vif->pkt_out),
vif->flags);
}
return 0;