linux-kernel - Re: [syzbot] BUG: sleeping function called from invalid context in ntfs_d

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Message-ID: <000000000000e46155062125a437@google.com>
Date: Mon, 02 Sep 2024 09:43:44 -0700
From: syzbot <syzbot+7f71f79bbfb4427b00e1@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org
Subject: Re: [syzbot] BUG: sleeping function called from invalid context in ntfs_d_hash

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***

Subject: BUG: sleeping function called from invalid context in ntfs_d_hash
Author: djahchankoike@...il.com

#syz test

d_hash is done while under "rcu-walk" and should not sleep,
__get_name() allocates using GFP_KERNEL, having the possibility
to sleep when under memory pressure. Change the allocation to
GFP_NOWAIT.

Signed-off-by: Diogo Jahchan Koike <djahchankoike@...il.com>
---
 fs/ntfs3/namei.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ntfs3/namei.c b/fs/ntfs3/namei.c
index f16d318c4372..d3d93651baa5 100644
--- a/fs/ntfs3/namei.c
+++ b/fs/ntfs3/namei.c
@@ -231,6 +231,7 @@ static int ntfs_rmdir(struct inode *dir, struct dentry *dentry)
 /*
  * ntfs_rename - inode_operations::rename
  */
+
 static int ntfs_rename(struct mnt_idmap *idmap, struct inode *dir,
 		       struct dentry *dentry, struct inode *new_dir,
 		       struct dentry *new_dentry, u32 flags)
@@ -395,7 +396,7 @@ static int ntfs_d_hash(const struct dentry *dentry, struct qstr *name)
 	/*
 	 * Try slow way with current upcase table
 	 */
-	uni = __getname();
+	uni = kmem_cache_alloc(names_cachep, GFP_NOWAIT);
 	if (!uni)
 		return -ENOMEM;
 
@@ -417,7 +418,7 @@ static int ntfs_d_hash(const struct dentry *dentry, struct qstr *name)
 	err = 0;
 
 out:
-	__putname(uni);
+	kmem_cache_free(names_cachep, uni);
 	return err;
 }
 
-- 
2.43.0