[merged mm-nonmm-stable] ipc-fix-to-protect-ipcs-lookups-using-rcu.patch removed from -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The quilt patch titled
     Subject: ipc: fix to protect IPCS lookups using RCU
has been removed from the -mm tree.  Its filename was
     ipc-fix-to-protect-ipcs-lookups-using-rcu.patch

This patch was dropped because it was merged into the mm-nonmm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Jeongjun Park <aha310510@gmail.com>
Subject: ipc: fix to protect IPCS lookups using RCU
Date: Thu, 24 Apr 2025 23:33:22 +0900

syzbot reported that it discovered a use-after-free vulnerability, [0]

[0]: https://lore.kernel.org/all/67af13f8.050a0220.21dd3.0038.GAE@google.com/

idr_for_each() is protected by rwsem, but this is not enough.  If it is
not protected by RCU read-critical region, when idr_for_each() calls
radix_tree_node_free() through call_rcu() to free the radix_tree_node
structure, the node will be freed immediately, and when reading the next
node in radix_tree_for_each_slot(), the already freed memory may be read.

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().

Link: https://lkml.kernel.org/r/20250424143322.18830-1-aha310510@gmail.com
Fixes: b34a6b1da371 ("ipc: introduce shm_rmid_forced sysctl")
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
Reported-by: syzbot+a2b84e569d06ca3a949c@syzkaller.appspotmail.com
Cc: Jeongjun Park <aha310510@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 ipc/shm.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/ipc/shm.c~ipc-fix-to-protect-ipcs-lookups-using-rcu
+++ a/ipc/shm.c
@@ -431,8 +431,11 @@ static int shm_try_destroy_orphaned(int
 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);
 }
 
_

Patches currently in -mm which might be from aha310510@gmail.com are

mm-vmalloc-fix-data-race-in-show_numa_info.patch