Re: KASAN: use-after-free Read in __rhashtable_lookup (2)

Sowmini Varadhan
2018-08-24T23:37:17Z

On (08/24/18 16:10), Dmitry Vyukov wrote:
> You need a colon after dup.

I see.

> But this can't possibly be a dup of that bug. That bug was fixed in February:

Apologies, I unknowingly made a mistake in my
syzbot-tiquette in that case,

I did not intend to *close* the bug as a dup, I was
merely trying to indicate that this is yet another
manifestation of the original report with subject
"KASAN: use-after-free Read in rds_find_bound"

All of these problems are happening because we are missing
a synchronize_net() in rds_release.

A full description of the race conditon can be found in
https://www.spinics.net/lists/netdev/msg475074.html

If rds_release is going to nuke the rds_socket
it needs to sychronize_net() with other threads that may be
looking up the bind_hash_table. If we dont do that,
all of these "use-after-free" races can happen.
As long as we dont have the synchronize_net() we are
missing a big (and standard) bit of RCU synchronization.

--Sowmini