[to-be-updated] hugetlbfs-emit-hugetlbfs_free_inode-from-destroy_inode.patch removed from -mm tree

[to-be-updated] hugetlbfs-emit-hugetlbfs_free_inode-from-destroy_inode.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: hugetlbfs: emit hugetlbfs_free_inode from ->destroy_inode()
has been removed from the -mm tree.  Its filename was
     hugetlbfs-emit-hugetlbfs_free_inode-from-destroy_inode.patch

This patch was dropped because an updated version will be issued

------------------------------------------------------
From: Joas Antonio dos Santos <joasantonio108@gmail.com>
Subject: hugetlbfs: emit hugetlbfs_free_inode from ->destroy_inode()
Date: Sat, 31 Oct 2026 16:06:02 +0000

hugetlbfs_free_inode() calls trace_hugetlbfs_free_inode(), and the
hugetlbfs__inode event class records inode->i_sb->s_dev.  ->free_inode()
runs from an RCU callback (destroy_inode() queues i_callback() with
call_rcu()), and Documentation/filesystems/porting.rst says that this
callback "is *NOT* ordered wrt superblock destruction; as the matter of
fact, the superblock and all associated structures might be already gone".
put_super() frees the superblock with call_rcu() followed by a workqueue
item (destroy_super_rcu() -> destroy_super_work()).  syzbot hit this with
the event enabled:

  BUG: KASAN: slab-use-after-free in trace_event_raw_event_hugetlbfs__inode+0x45b/0x4c0 include/trace/events/hugetlbfs.h:36
  Read of size 4 at addr ffff888038850010 by task syz-executor952/6134
   hugetlbfs_free_inode+0x15e/0x1f0 fs/hugetlbfs/inode.c:1182
   i_callback+0x46/0x80 fs/inode.c:317
   rcu_do_batch kernel/rcu/tree.c:2650 [inline]
   rcu_core+0x5f0/0x1220 kernel/rcu/tree.c:2919
  Allocated by task 6134:
   alloc_super fs/super.c:326 [inline]
   sget_fc+0x1ba/0x1f60 fs/super.c:874
   hugetlbfs_get_tree+0x1e7/0x2b0 fs/hugetlbfs/inode.c:1431
  Freed by task 855:
   kfree+0x22b/0x6d0 mm/slub.c:6923
   process_one_work+0xac7/0x1b10 kernel/workqueue.c:3495

Emit the event from hugetlbfs_destroy_inode() instead.  destroy_inode()
calls ->destroy_inode() synchronously, before it queues the RCU callback,
while the superblock is still alive; hugetlbfs_destroy_inode() already
dereferences inode->i_sb there.  ->free_inode() is left with only the
kmem_cache_free().

Link: https://lore.kernel.org/20261031-b4-hugetlbfs-trace-v1-1-4ec8d02a30cc@gmail.com
Fixes: 014ad7c42a69 ("hugetlbfs: use tracepoints in hugetlbfs functions.")
Signed-off-by: Joas Antonio dos Santos <joasantonio108@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: <syzbot+91e1fc35f51774c479b2@syzkaller.appspotmail.com>
Closes: https://lore.kernel.org/all/6ae27525.5451848c.f7707.0001.GAE@google.com/
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@kernel.org>
Cc: Hongbo Li <lihongbo22@huawei.com>
Cc: <stable@vger.kernel.org>
---

 fs/hugetlbfs/inode.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/fs/hugetlbfs/inode.c~hugetlbfs-emit-hugetlbfs_free_inode-from-destroy_inode
+++ a/fs/hugetlbfs/inode.c
@@ -1179,12 +1179,16 @@ static struct inode *hugetlbfs_alloc_ino
 
 static void hugetlbfs_free_inode(struct inode *inode)
 {
-	trace_hugetlbfs_free_inode(inode);
 	kmem_cache_free(hugetlbfs_inode_cachep, HUGETLBFS_I(inode));
 }
 
 static void hugetlbfs_destroy_inode(struct inode *inode)
 {
+	/*
+	 * Not in ->free_inode(): that runs from an RCU callback, when the
+	 * superblock the event reads may already be freed.
+	 */
+	trace_hugetlbfs_free_inode(inode);
 	hugetlbfs_inc_free_inodes(HUGETLBFS_SB(inode->i_sb));
 }
 
_

Patches currently in -mm which might be from joasantonio108@gmail.com are