linux-kernel - [PATCH] sched_ext: create_dsq: Return -EEXIST on duplicate request

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <20250325224041.14088-1-jake@hillion.co.uk>
Date: Tue, 25 Mar 2025 22:41:52 +0000
From: Jake Hillion <jake@...lion.co.uk>
To: tj@...nel.org
Cc: arighi@...dia.com, changwoo@...lia.com, sched-ext@...a.com, linux-kernel@...r.kernel.org, Jake Hillion <jake@...lion.co.uk>
Subject: [PATCH] sched_ext: create_dsq: Return -EEXIST on duplicate request

create_dsq and therefore the scx_bpf_create_dsq kfunc currently silently
ignore duplicate entries. As a sched_ext scheduler is creating each DSQ
for a different purpose this is surprising behaviour.

Replace rhashtable_insert_fast which ignores duplicates with
rhashtable_lookup_insert_fast that reports duplicates (though doesn't
return their value). The rest of the code is structured correctly and
this now returns -EEXIST.

Tested by adding an extra scx_bpf_create_dsq to scx_simple. Previously
this was ignored, now init fails with a -17 code. Also ran scx_lavd
which continued to work well.

Signed-off-by: Jake Hillion <jake@...lion.co.uk>
---
 kernel/sched/ext.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 21575d39c376..b47be2729ece 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4171,8 +4171,8 @@ static struct scx_dispatch_q *create_dsq(u64 dsq_id, int node)

 	init_dsq(dsq, dsq_id);

-	ret = rhashtable_insert_fast(&dsq_hash, &dsq->hash_node,
-				     dsq_hash_params);
+	ret = rhashtable_lookup_insert_fast(&dsq_hash, &dsq->hash_node,
+					    dsq_hash_params);
 	if (ret) {
 		kfree(dsq);
 		return ERR_PTR(ret);
-- 
2.47.2