netdev - [v2 PATCH] rhashtable: Fix rhashtable_try

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Z4FXs8vAtitHIJyl@gondor.apana.org.au>
Date: Sat, 11 Jan 2025 01:24:03 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Michael Kelley <mhklinux@...look.com>
Cc: Breno Leitao <leitao@...ian.org>,
	"saeedm@...dia.com" <saeedm@...dia.com>,
	"tariqt@...dia.com" <tariqt@...dia.com>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Graf <tgraf@...g.ch>, Tejun Heo <tj@...nel.org>,
	Hao Luo <haoluo@...gle.com>, Josh Don <joshdon@...gle.com>,
	Barret Rhoden <brho@...gle.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [v2 PATCH] rhashtable: Fix rhashtable_try_insert test

On Fri, Jan 10, 2025 at 04:59:28PM +0000, Michael Kelley wrote:
>
> This patch fixes the problem I saw with VMs in the Azure cloud.  Thanks!

Sorry, but the test on data is needed after all (it was just
buggy).  Otherwise we will break rhlist.  So please test this
patch instead.

---8<---
The test on whether rhashtable_insert_one did an insertion relies
on the value returned by rhashtable_lookup_one.  Unfortunately that
value is overwritten after rhashtable_insert_one returns.  Fix this
by saving the old value.

Also simplify the test as only data == NULL matters.

Reported-by: Michael Kelley <mhklinux@...look.com>
Fixes: e1d3422c95f0 ("rhashtable: Fix potential deadlock by moving schedule_work outside lock")
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index bf956b85455a..e36b36f3146d 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -611,17 +611,20 @@ static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
 			new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
 			data = ERR_PTR(-EAGAIN);
 		} else {
+			void *odata;
+
 			flags = rht_lock(tbl, bkt);
 			data = rhashtable_lookup_one(ht, bkt, tbl,
 						     hash, key, obj);
 			new_tbl = rhashtable_insert_one(ht, bkt, tbl,
 							hash, obj, data);
+			odata = data;
 			if (PTR_ERR(new_tbl) != -EEXIST)
 				data = ERR_CAST(new_tbl);
 
 			rht_unlock(tbl, bkt, flags);
 
-			if (PTR_ERR(data) == -ENOENT && !new_tbl) {
+			if (odata && !new_tbl) {
 				atomic_inc(&ht->nelems);
 				if (rht_grow_above_75(ht, tbl))
 					schedule_work(&ht->run_work);
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt