Re: [syzbot] Re: [syzbot] [fs?] possible deadlock in __simple_recursive_removal

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Subject: Re: [syzbot] [fs?] possible deadlock in __simple_recursive_removal
Author: lizhi.xu@windriver.com

#syz test

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index 760437a91648..64dc551681b9 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -734,7 +734,7 @@ static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
 	case 3:
 		/* Delete this handler. */
 		inode = d_inode(inode->i_sb->s_root);
-		inode_lock(inode);
+		inode_lock_nested(inode, I_MUTEX_PARENT);
 
 		/*
 		 * In order to add new element or remove elements from the list
@@ -803,7 +803,7 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 		e->interp_file = f;
 	}
 
-	inode_lock(d_inode(root));
+	inode_lock_nested(d_inode(root), I_MUTEX_PARENT);
 	dentry = lookup_noperm(&QSTR(e->name), root);
 	err = PTR_ERR(dentry);
 	if (IS_ERR(dentry))