linux-kernel - Re: [syzbot] [v9fs?] WARNING in v9fs_begin

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Message-ID: <tencent_5D5C3C9B368696CC37D64A8A755F77196609@qq.com>
Date: Wed, 14 Aug 2024 17:26:52 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+0b74d367d6e80661d6df@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [v9fs?] WARNING in v9fs_begin_writeback

debug

#syz test: upstream c0ecd6388360

diff --git a/fs/9p/vfs_dir.c b/fs/9p/vfs_dir.c
index e0d34e4e9076..cb511d49e35a 100644
--- a/fs/9p/vfs_dir.c
+++ b/fs/9p/vfs_dir.c
@@ -218,8 +218,10 @@ int v9fs_dir_release(struct inode *inode, struct file *filp)
 		if ((S_ISREG(inode->i_mode)) && (filp->f_mode & FMODE_WRITE))
 			retval = filemap_fdatawrite(inode->i_mapping);
 
+		printk("fid: %p, %s\n", fid, __func__);
 		spin_lock(&inode->i_lock);
-		hlist_del(&fid->ilist);
+		if (refcount_read(&fid->count) == 1)
+			hlist_del(&fid->ilist);
 		spin_unlock(&inode->i_lock);
 		put_err = p9_fid_put(fid);
 		retval = retval < 0 ? retval : put_err;
diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 348cc90bf9c5..acee5f6570a5 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -52,6 +52,7 @@ int v9fs_file_open(struct inode *inode, struct file *file)
 		omode = v9fs_uflags2omode(file->f_flags,
 					v9fs_proto_dotu(v9ses));
 	fid = file->private_data;
+	printk("fid: %p, %s\n", fid, __func__);
 	if (!fid) {
 		fid = v9fs_fid_clone(file_dentry(file));
 		if (IS_ERR(fid))
@@ -80,6 +81,8 @@ int v9fs_file_open(struct inode *inode, struct file *file)
 
 		file->private_data = fid;
 	}
+	else
+		p9_fid_get(fid);
 
 #ifdef CONFIG_9P_FSCACHE
 	if (v9ses->cache & CACHE_FSCACHE)