Re: [PATCH] wireguard: Mark concurrent accesses to reused indices

[Zhu Jun]

Hi,

The access pair addressed by this patch was observed at runtime by
syzbot/KCSAN. The report is available here:
https://syzbot.org/bug?extid=54fe9e7dbf4babbaeea3

It records a 4-byte write in wg_index_hashtable_insert()
(drivers/net/wireguard/peerlookup.c:132) racing with a 4-byte read in
wg_index_hashtable_lookup() (drivers/net/wireguard/peerlookup.c:211).

I have not reproduced the race locally or verified at runtime that this
patch eliminates the report. My local validation was limited to W=1
builds of the affected object on x86-64 and i386, including an x86-64
KCSAN_STRICT build. I have not demonstrated a functional failure such as
a crash or incorrect packet processing beyond the reported data race.

If another revision is needed for other reasons, I will include this
report and the validation limitations in the commit message.

Thanks,
Zhu Jun