linux-kernel - [PATCH v2] ipc: fix to protect IPCS lookups using RCU

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>] [day] [month] [year] [list]

Message-ID: <20250422124843.17188-1-aha310510@gmail.com>
Date: Tue, 22 Apr 2025 21:48:43 +0900
From: Jeongjun Park <aha310510@...il.com>
To: Liam.Howlett@...cle.com,
	akpm@...ux-foundation.org
Cc: lorenzo.stoakes@...cle.com,
	willy@...radead.org,
	linux-kernel@...r.kernel.org,
	syzbot+a2b84e569d06ca3a949c@...kaller.appspotmail.com,
	Jeongjun Park <aha310510@...il.com>
Subject: [PATCH v2] ipc: fix to protect IPCS lookups using RCU

idr_for_each() is protected by rwsem, but this is not enough. If it is not
protected by the RCU read-critical region, when we call radix_tree_node_free()
via call_rcu() to free the struct radix_tree_node, the node will be freed
immediately, and when we read the next node in radix_tree_for_each_slot(),
we can read the already freed memory.

Therefore, we need to add code to make sure that idr_for_each() is protected
within the RCU read-critical region when we call it in shm_destroy_orphaned().

Reported-by: syzbot+a2b84e569d06ca3a949c@...kaller.appspotmail.com
Fixes: b34a6b1da371 ("ipc: introduce shm_rmid_forced sysctl")
Cc: Matthew Wilcox <willy@...radead.org>
Signed-off-by: Jeongjun Park <aha310510@...il.com>
---
v2: Change description and coding style
---
 ipc/shm.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/ipc/shm.c b/ipc/shm.c
index 99564c870084..492fcc699985 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -431,8 +431,11 @@ static int shm_try_destroy_orphaned(int id, void *p, void *data)
 void shm_destroy_orphaned(struct ipc_namespace *ns)
 {
 	down_write(&shm_ids(ns).rwsem);
-	if (shm_ids(ns).in_use)
+	if (shm_ids(ns).in_use) {
+		rcu_read_lock();
 		idr_for_each(&shm_ids(ns).ipcs_idr, &shm_try_destroy_orphaned, ns);
+		rcu_read_unlock();
+	}
 	up_write(&shm_ids(ns).rwsem);
 }
 
--